Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “termination”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1990

Lambda nutR mutations convert HK022 Nun protein from a transcription termination factor to a suppressor of termination.

The Nun protein of the lambdoid phage HK022 blocks lambda growth by terminating transcription at (or near) the lambda nut sites. An HK022 lysogen carrying a fusion of the lambda pR promoter and nutR site to a gal operon that lacks its own promoter is, therefore, Gal-. To characterize the target of Nun action, spontaneous Gal+ revertants of this strain were isolated and characterized. Two cis-acting mutations are located in the fusion and represent transversions of conserved nucleotides within the boxA sequence (CGCTCTTA) of nutR. One mutation, (CTCTCTTA), is identical with boxA5. The second, boxA16 (CGCTATTA), has not been reported previously. In the absence of Nun, both boxA mutants reduce gal expression. Analysis of in vivo fusion RNA indicates that the mutations increase termination at or near tR1, a rho-dependent lambda terminator located upstream from the fusion point. In contrast to the nutR+ fusion, Nun stimulates gal expression in the boxA mutants by suppressing transcription termination in the tR1 region. Nun antitermination, however, does not extend to distal terminators. The lambda N-function also suppresses termination at or near tR1 in the mutant fusions. N fails to suppress terminators distal to tR1 in the boxA5 fusion, but displays persistent antitermination activity in the boxA16 fusion. A similar reversal of Nun activity occurs when wild-type fusions are introduced into nusA1, nusB5 or nusE71 hosts. We therefore suggest that Nun and N can interact with RNA polymerase in the absence of wild-type boxA, nusA, nusB or nusE, but that the complex formed with mutant components differs functionally from wild-type.

Bacteriophage lambda↗
PubMed2006

Membrane biogenesis of subunit II of cytochrome bo oxidase: contrasting requirements for insertion of N-terminal and C-terminal domains.

The membrane assembly of the respiratory complexes requires the membrane insertases Oxa1 in mitochondria and YidC in bacteria. Oxa1 is responsible for the insertion of the mitochondrial cytochrome c oxidase subunit II (CoxII). Here, we investigated whether YidC, the bacterial Oxa1 homolog, plays a crucial role in the assembly of the bacterial subunit II (CyoA) of cytochrome bo oxidase. CyoA spans the membrane twice and is made with a cleavable signal peptide. We find that translocation of the short N-terminal domain of CyoA is YidC-dependent. In contrast, both the SecA/SecYEG complex and YidC are required for translocation of the large C-terminal domain. By studying the N-terminal domain of CyoA alone, we find that translocation is unaffected when SecE is depleted, suggesting that the YidC insertase on its own catalyzes membrane insertion of the N-terminal region of CyoA. Strikingly, we find that the translocation of the N-terminal domain is a prerequisite for translocation of the C-terminal domain in the full-length CyoA protein because translocation of the large C-terminal domain alone in a truncated CyoA derivative was observed in the absence of YidC. This work shows that the distinct domains of CyoA have different translocation requirements (YidC only and Sec/YidC) and confirms that the membrane biogenesis of subunit II of cytochrome oxidase in bacteria and mitochondria have conserved features.

Adenosine Triphosphatases↗
PubMed2003

N-terminal acetyltransferases and sequence requirements for N-terminal acetylation of eukaryotic proteins.

N(alpha)-terminal acetylation occurs in the yeast Saccharomyces cerevisiae by any of three N-terminal acetyltransferases (NAT), NatA, NatB, and NatC, which contain Ard1p, Nat3p and Mak3p catalytic subunits, respectively. The N-terminal sequences required for N-terminal acetylation, i.e. the NatA, NatB, and NatC substrates, were evaluated by considering over 450 yeast proteins previously examined in numerous studies, and were compared to the N-terminal sequences of more than 300 acetylated mammalian proteins. In addition, acetylated sequences of eukaryotic proteins were compared to the N termini of 810 eubacterial and 175 archaeal proteins, which are rarely acetylated. Protein orthologs of Ard1p, Nat3p and Mak3p were identified with the eukaryotic genomes of the sequences of model organisms, including Caenorhabditis elegans, Drosophila melanogaster, Arabidopsis thaliana, Mus musculus and Homo sapiens. Those and other putative acetyltransferases were assigned by phylogenetic analysis to the following six protein families: Ard1p; Nat3p; Mak3p; CAM; BAA; and Nat5p. The first three families correspond to the catalytic subunits of three major yeast NATs; these orthologous proteins were identified in eukaryotes, but not in prokaryotes; the CAM family include mammalian orthologs of the recently described Camello1 and Camello2 proteins whose substrates are unknown; the BAA family comprise bacterial and archaeal putative acetyltransferases whose biochemical activity have not been characterized; and the new Nat5p family assignment was on the basis of putative yeast NAT, Nat5p (YOR253W). Overall patterns of N-terminal acetylated proteins and the orthologous genes possibly encoding NATs suggest that yeast and higher eukaryotes have the same systems for N-terminal acetylation.

Acetylation↗
PubMed1990

Carboxy-terminal sequencing: formation and hydrolysis of C-terminal peptidylthiohydantoins.

Proteins and peptides can be sequenced from the carboxy terminus with isothiocyanate reagents to produce amino acid thiohydantoin derivatives. Previous studies in our laboratory indicated that the use of trimethylsilyl isothiocyanate (TMS-ITC) as a coupling reagent significantly improved the yields and reaction conditions and reduced the number of complicating side products [Hawke et al. (1987) Anal. Biochem. 166, 298]. The present study further explores the conditions for formation of the peptidylthiohydantoins by TMS-ITC and examines the cleavage of these peptidylthiohydantoin derivatives into a shortened peptide and thiohydantoin amino acid derivative. Schizophrenia-related peptide (Thr-Val-Leu) was used as a model peptide and was treated with acetic anhydride and TMS-ITC at 50 degrees C for 30 min, and the peptidylthiohydantoin derivatives were isolated by reverse-phase HPLC and characterized by FAB-MS. The purified derivatives were subjected to a variety of cleavage conditions, and rate constants for hydrolysis were determined. Hydrolysis with acetohydroxamate as reported originally by Stark [(1968) Biochemistry 7, 1796] was found to give excellent cleavage of the terminal thiohydantoin amino acid, but also led to the formation of stable hydroxamate esters of the shortened peptide which are poorly suited for subsequent rounds of degradation. Hydrolysis with 2% aqueous triethylamine under mild conditions (1-5 min at 50 degrees C) was found to be more suitable for carboxy-terminal sequence analysis by the thiocyanate method. The shortened peptide, which could be isolated and subjected to a second round of degradation, and the released thiohydantoin amino acid are formed in good yield (90-100%). Several other small peptides containing 15 different C-terminal amino acid side chains were also investigated in order to examine any interfering reactions that might occur when these side chains are encountered in a stepwise degradation using the thiocyanate chemistry. Quantitative yields of peptidylthiohydantoins were obtained for all the amino acids examined with the following exceptions: low yields were obtained for C-terminal Glu or Thr, and no peptidylthiohydantoins were obtained for C-terminal Pro or Asp. Asparagine was found to form cyclic imides (64%) at the penultimate position (C-2) during hydrolysis of the peptidylthiohydantoins by 2% aqueous triethylamine. Cleavage of C-terminal Asn under these conditions led to the formation of the expected shortened peptide (69%), but also to the formation of a shortened peptide (31%) with a C-terminal amide. Problems with Glu and Thr could be solved by minimizing the reaction time with acetic anhydride.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed2002

Solution structure of N-terminal SH3 domain of Vav and the recognition site for Grb2 C-terminal SH3 domain.

The three-dimensional structure of the N-terminal SH3 domain (residues 583-660) of murine Vav, which contains a tetra-proline sequence (Pro 607-Pro 610), was determined by NMR. The solution structure of the SH3 domain shows a typical SH3 fold, but it exists in two conformations due to cis-trans isomerization at the Gly614-Pro615 bond. The NMR structure of the P615G mutant, where Pro615 is replaced by glycine, reveals that the tetra-proline region is inserted into the RT-loop and binds to its own SH3 structure. The C-terminal SH3 domain of Grb2 specifically binds to the trans form of the N-terminal SH3 domain of Vav. The surface of Vav N-terminal SH3 which binds to Grb2 C-terminal SH3 was elucidated by chemical shift mapping experiments using NMR. The surface does not involve the tetra-proline region but involves the region comprising the n-src loop, the N-terminal and the C-terminal regions. This surface is located opposite to the tetra-proline containing region, consistent with that of our previous mutagenesis studies.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Functions of the C-terminal domain of CTP: phosphocholine cytidylyltransferase. Effects of C-terminal deletions on enzyme activity, intracellular localization and phosphorylation potential.

The role of the C-terminal domain of CTP: phosphocholine cytidylyltransferase (CT) was explored by the creation of a series of deletion mutations in rat liver cDNA, which were expressed in COS cells as a major protein component. Deletion of up to 55 amino acids from the C-terminus had no effect on the activity of the enzyme, its stimulation by lipid vesicles or on its intracellular distribution between soluble and membrane-bound forms. However, deletion of the C-terminal 139 amino acids resulted in a 90% decrease in activity, loss of response to lipid vesicles and a significant decrease in the fraction of membrane-bound enzyme. Identification of the domain that is phosphorylated in vivo was determined by analysis of 32P-labelled CT mutants and by chymotrypsin proteolysis of purified CT that was 32P-labelled in vivo. Phosphorylation was restricted to the C-terminal 52 amino acids (domain P) and occurred on multiple sites. CT phosphorylation in vitro was catalysed by casein kinase II, cell division control 2 kinase (cdc2 kinase), protein kinases C alpha and beta II, and glycogen synthase kinase-3 (GSK-3), but not by mitogen-activated kinase (MAP kinase). Casein kinase II phosphorylation was directed exclusively to Ser-362. The sites phosphorylated by cdc2 kinase and GSK-3 were restricted to several serines within three proline-rich motifs of domain P. Sites phosphorylated in vitro by protein kinase C, on the other hand, were distributed over the N-terminal catalytic as well as the C-terminal regulatory domain. The stoichiometry of phosphorylation catalysed by any of these kinases was less than 0.2 mol P/mol CT, and no effects on enzyme activity were detected. This study supports a tripartite structure for CT with an N-terminal catalytic domain and a C-terminal regulatory domain comprised of a membrane-binding domain (domain M) and a phosphorylation domain (domain P). It also identifies three kinases as potential regulators in vivo of CT, casein kinase II, cyclin-dependent kinase and GSK-3.

Amino Acid Sequence↗
PubMed1981

Terminal proteins and short inverted terminal repeats of the small Bacillus bacteriophage genomes.

The genome of Bacillus phage phi 29 contains covalently linked protein at both ends. These DNA terminal proteins are essential for phi 29 DNA replication. We have isolated phi 29 terminal protein from each end separately and compared their two-dimensional peptide maps. Our results showed the two proteins to be identical. The DNAs of four phages examined (phi 15, Nf, M2Y, and GA-1) also contain protein at both ends of the DNA molecules. The chymotryptic peptide maps of these DNA terminal proteins have been compared with the map of the phi 29 terminal protein. Despite the similarities in molecular size, peptide maps of the terminal proteins show clear differences among the unrelated phages. These results are consistent with the idea that the terminal proteins are encoded by viral DNA rather than by the host chromosome. We have also determined the nucleotide sequences of the termini of four phage DNAs and compared them with the sequence of phi 29 DNA. The sequence data indicate that all of these phages DNA contain short inverted terminal repeats: 5'A-A-A-G-T-A for phi 29 and phi 15, 5' A-A-A-G-T-A-A-G for Nf and M2Y, and 5' A-A-A-T-A-G-A for GA-1.

Bacteriophages↗
PubMed1995

The 3'-terminal exon of the family of steroid and phenol sulfotransferase genes is spliced at the N-terminal glycine of the universally conserved GXXGXXK motif that forms the sulfonate donor binding site.

The guinea pig estrogen sulfotransferase gene has been cloned and compared to three other cloned steroid and phenol sulfotransferase genes (human estrogen sulfotransferase, human phenol sulfotransferase, and guinea pig 3 alpha-hydroxysteroid sulfotransferase). The four sulfotransferase genes demonstrate a common outstanding feature: the splice sites for their 3'-terminal exons are identically located. That is, the 3'-terminal exon splice sites involve a glycine that constitutes the N-terminal glycine of an invariably conserved GXXGXXK motif present in all steroid and phenol sulfotransferases for which primary structures are known. This consistency strongly suggests that all steroid and phenol sulfotransferase genes will be similarly spliced. The GXXGXXK motif forms the active binding site for the universal sulfonate donor 3'-phosphoadenosine 5'-phosphosulfate. Amino acid sequence alignment of 19 cloned steroid and phenol sulfotransferases starting with the GXXGXXK motif indicates that the 3'-terminal exon for each steroid and phenol sulfotransferase gene encodes a similarly sized C-terminal fragment of the protein. Interestingly, on further analysis of the alignment, three distinct amino acid sequence patterns emerge. The presence of the conserved functional GXXGXXK motif suggests that the protein domains encoded by steroid and phenol sulfotransferase 3'-terminal exons have evolved from a common ancestor. Furthermore, it is hypothesized that during the course of evolution, the 3'-terminal exon further diverged into at least three sulfotransferase subdivisions: a phenol or aryl group, an estrogen or phenolic steroid group, and a neutral steroid group.

Amino Acid Sequence↗
PubMed1996

C-terminal trimerization, but not N-terminal trimerization, of the reovirus cell attachment protein Is a posttranslational and Hsp70/ATP-dependent process.

The C-terminal globular head of the lollipop-shaped final sigma1 protein of reovirus is responsible for interaction with the host cell receptor. Like the N-terminal fibrous tail, it has its own trimerization domain. Whereas N-terminal trimerization (formation of a triple alpha-helical coiled coil) occurs at the level of polysomes (i.e. cotranslationally) and is ATP-independent, C-terminal trimerization is a posttranslational event that requires ATP. Coprecipitation experiments using anti-Hsp70 antibodies and truncated final sigma1 proteins synthesized in vitro revealed that only regions downstream of the N-terminal alpha-helical coiled coil were associated with Hsp70. Hsp70 was also found to be associated with nascent final sigma1 chains on polysomes as well as with immature postribosomal final sigma1 trimers (hydra-like intermediates with assembled N termini and unassembled C termini). These latter structures were true intermediates in the final sigma1 biogenetic pathway since they could be chased into mature final sigma1 trimers with the release of Hsp70. Thus, unlike N-terminal trimerization, C-terminal trimerization is Hsp70- and ATP-dependent. The involvement of two mechanistically distinct oligomerization events for the same molecule, one cotranslational and one posttranslational, may represent a common approach to the generation of oligomeric proteins in the cytosol.

Adenosine Triphosphate↗
PubMed1997

C-terminal mutation of G protein beta subunit affects differentially extracellular signal-regulated kinase and c-Jun N-terminal kinase pathways in human embryonal kidney 293 cells.

G protein beta and gamma subunits (Gbeta and Ggamma) form a complex that is involved in various signaling pathways. We reported that the C-terminal 10 amino acids of Gbeta are required for association with Ggamma (Yamauchi, J., Kaziro, Y., and Itoh, H. (1995) Biochem. Biophys. Res. Commun., 214, 694-700). To evaluate further the significance of the C-terminal region of Gbeta in the formation of a Gbetagamma complex and its signal transduction, we constructed several C-terminal mutants and expressed them in human embryonal kidney 293 cells. The mutant lacking the C-terminal 2 amino acids (DeltaC2) failed to associate with Ggamma, whereas deletion of the C-terminal amino acid (DeltaC1), replacement of Trp at -2 position by Ala (W339A), and addition of six histidines ((His)6) at the C terminus did not affect the association with Ggamma. We also studied the effect of these mutations on the activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK). Co-expression of the DeltaC2 or (His)6 mutant with Ggamma did not activate MAPK/ERK at all, whereas the DeltaC1 or W339A mutant showed the MAPK/ERK activation. The JNK/SAPK activity was stimulated by the W339A, DeltaC2, or (His)6 mutant, but not by the DeltaC1 mutant. These results suggest that the C-terminal region of Gbeta participates differentially in the signaling for MAPK/ERK and JNK/SAPK activations in mammalian cells.

Amino Acid Sequence↗
PubMed2002

Distinct roles of the N-terminal-binding domain and the C-terminal-solubilizing domain of alpha-synuclein, a molecular chaperone.

alpha-Synuclein, an acidic neuronal protein of 140 amino acids, is extremely heat-resistant and is natively unfolded. Recent studies have demonstrated that alpha-synuclein has chaperone activity both in vitro and in vivo, and that this activity is lost upon removing its C-terminal acidic tail. However, the detailed mechanism of the chaperone action of alpha-synuclein remains unknown. In this study, we investigated the molecular mechanism of the chaperone action of alpha-synuclein by analyzing the roles of its N-terminal and C-terminal domains. The N-terminal domain (residues 1-95) was found to bind to substrate proteins to form high molecular weight complexes, whereas the C-terminal acidic tail (residues 96-140) appears to be primarily involved in solubilizing the high molecular weight complexes. Because the substrate-binding domain and the solubilizing domain for chaperone function are well separated in alpha-synuclein, the N-terminal-binding domain can be substituted by other proteins or peptides. Interestingly, the resultant engineered chaperone proteins appeared to display differential efficiency and specificity in terms of the chaperone function, which depended upon the nature of the binding domain. This finding implies that the C-terminal acidic tail of alpha-synuclein can be fused with other proteins or peptides to engineer synthetic chaperones for specific purposes.

Animals↗
PubMed2004

The C-terminal domain of pediocin-like antimicrobial peptides (class IIa bacteriocins) is involved in specific recognition of the C-terminal part of cognate immunity proteins and in determining the antimicrobial spectrum.

The pediocin-like bacteriocins contain two domains: a cationic N-terminal beta-sheet domain that mediates binding of the bacteriocin to the target cell surface and a more hydrophobic C-terminal hairpin-like domain that penetrates into the hydrophobic part of the target cell membrane. The two domains are joined by a hinge, which enables movement of the domains relative to each other. In this study, 12 different hybrid bacteriocins were constructed by exchanging domains between 5 different bacteriocins. The hybrid bacteriocins were by and large highly potent (i.e. similar potencies as the parental bacteriocins) when constructed such that the recombination point was in the hinge region, indicating that the two domains function independently. The use of optimal recombination points was, however, crucial. Shifting the recombination point just one residue from the hinge could reduce the activity of the hybrid by 3-4 orders of magnitude. Most interestingly, the active hybrids displayed target cell specificities similar to those of the parental bacteriocin from which their membrane-penetrating C-terminal hairpin domain was derived. The results also indicate that the negatively charged aspartate reside in the hinge of most pediocin-like bacteriocins interacts with the C-terminal hairpin domain, perhaps by interacting with the positively charged residue that is present at one of the last three positions in the C-terminal end of most pediocin-like bacteriocins. Bacteria that produce pediocin-like bacteriocins also produce a cognate immunity protein that protects the producer from being killed by its own bacteriocin. Four different active hybrid immunity proteins constructed by exchanging regions between three different immunity proteins were tested for their ability to confer immunity to the hybrid bacteriocins. The results showed that the C-terminal half of the immunity proteins contains a region that directly or indirectly specifically recognizes the membrane-penetrating C-terminal hairpin domain of pediocin-like bacteriocins. The implications these results have on how pediocin-like bacteriocins and their immunity proteins interact with cellular specificity determinants (for instance a putative bacteriocin receptor) are discussed.

Amino Acid Sequence↗
PubMed2005

Different roles of N-terminal and C-terminal halves of HIRA in transcription regulation of cell cycle-related genes that contribute to control of vertebrate cell growth.

We reported previously that chicken HIRA, a homolog of Saccharomyces cerevisiae transcriptional co-repressors Hir1p and Hir2p, possesses seven WD dipeptide motifs and an LXXLL motif in its N-terminal and C-terminal halves, respectively, required for transcription regulations. Here, by using the gene targeting technique, we generated the homozygous HIRA-deficient DT40 mutant DeltaHIRA. The HIRA deficiency caused slightly delayed cell growth and affected the opposite transcriptions of cell cycle-related genes, i.e. repressions for P18, CDC25B, and BCL-2, activations for P19 and cyclin A, and histones H2A, H2B, H3, and H4. These altered expressions were completely revived by the artificial stable expression of hemagglutinin-tagged HIRA in DeltaHIRA. The ability to rescue the delayed growth rate was preferentially aided by the N-terminal half instead of the C-terminal half. We cloned the chicken P18 genomic DNA, and we established that its promoter was located surrounding the sequence GCGGGCGC at positions -1157 to -1150. Chromatin immunoprecipitation assay revealed that the N-terminal half interacted directly or indirectly with the putative promoter region of the p18 gene, resulting in up-regulation of the gene. These results indicated that the N-terminal half of HIRA should contribute positively to the growth rate via up-regulation of a set of cell cycle-related genes, whereas the C-terminal half down-regulated another set of them without exhibiting any effect on the cell growth.

Amino Acid Motifs↗
PubMed1996

The amino-terminal domain of the transcription termination factor TTF-I causes protein oligomerization and inhibition of DNA binding.

The transcription termination factor TTF-I binds specifically to an 18 bp DNA element in the murine ribosomal gene spacer and mediates termination of RNA polymerase I transcription. In this study, we have compared DNA binding and termination activity of recombinant full-length TTF-I (TTF-Ip130) with two deletion mutants lacking 184 and 322 N-terminal amino acids, respectively. All three proteins exhibit similar termination activity, but the DNA binding of TTF-Ip130 is at least one order of magnitude lower than that of the deletion mutants, indicating that the N-terminus represses the interaction of TTF-I with DNA. The inhibitory effect of the N-terminus can be transferred to a heterologous DNA binding domain and is separable from other activities of TTF-I. We show by several methods that TTF-Ip130, the N-terminal domain alone, and fusions of the N-terminus with the DNA binding domain of Oct2.2 form stable oligomers in solution. Thus, in contrast to previous studies suggesting that activation of TTF-I occurs through proteolysis, we demonstrate that full-length TTF-I mediates termination of rDNA transcription in vivo and in vitro and that the oligomerization state of TTF-I may influence its DNA binding activity.

Animals↗
PubMed1988

Amino-terminal and carboxyl-terminal half-molecules of ovotransferrin: preparation by a novel procedure and their interactions.

The amino- (N-) and carboxyl- (C-)terminal half-molecules of ovotransferrin were prepared by a novel procedure. The trypsin-nicked ovotransferrin (Ikeda et al. (1985) FEBS Lett. 182, 305-309), in which the two half-molecules interact non-covalently forming a stable dimer, was purified by gel filtration and anion-exchange column chromatography. By subsequent cation-exchange chromatography, the nicked form was distinctly separated into an equivalent amount of the N-terminal and C-terminal half-molecules. Analyses of the N-terminal and C-terminal sequences indicated that the N-terminal and C-terminal half-molecules comprised the alignments of residues 1-332 and 342-686 of ovotransferrin, respectively. Anion-exchange chromatography, gel filtration chromatography, and non-denaturing polyacrylamide gel electrophoresis revealed that the isolated half-molecules had the ability to re-associate in solution. The contents of alpha-helix and beta-sheet of the two half-molecules, as determined by circular dichroism (CD) spectra, were very similar to those of intact ovotransferrin. No prominent alteration in the secondary structure of the two half-molecules was induced by the re-association.

Amino Acids↗
PubMed1981

Interaction of the N-terminal and C-terminal domains of elongation factor G on formation of complexes with guanyl nucleotides.

Polarized fluorescence studies of interaction between guanyl nucleotides (GTP and GDP) and elongation factor G and its N-terminal tryptic fragment T*/s, carrying a fluorescent group (aminorhodamine B) at the exposed cysteine residue, has shown that binding on nucleotides by an intact EF-G molecule at neutral pH essentially affects the mobility of the fluorescent group. GTP binding changes its relaxation properties to a greater extent than GDP binding. At the same time it was demonstrated that the spectrum of relaxation time of the fluorescent group practically does not change on binding of nucleotides by the N-terminal fragment T*/2 (in the absence of the C-terminal domain) or in the case when the three-dimensional structure of the intact EF-G molecule is destabilized (pH 10). Comparison of the relaxation properties of EF-G and its N-terminal fragment T*/2, carrying a fluorescent group at the exposed cysteine residue, at pH 7.5 and 10, indicates that the C-terminal domain is involved in the formation of the close environment of the exposed cysteine residue located in the N-terminal part of EF-G. A conclusion is drawn on the nucleotide-induced influence of the C-terminal domain on a change of the exposed cysteine residue environment on guanyl nucleotide binding with EF-G at neutral pH and a hypothetical model of the EF-G molecule is proposed.

Fluorescence Polarization↗
PubMed1994

Overexpression of C-terminally but not N-terminally truncated Myb induces fibrosarcomas: a novel nonhematopoietic target cell for the myb oncogene.

The myb oncogene encodes a DNA-binding transcriptional transactivator which can become a hematopoietic cell-transforming protein following the deletion of amino acid sequences from either its amino or carboxyl terminus. Although a number of hematopoietic tumors express terminally deleted variants of Myb, the involvement of truncated Myb in nonhematopoietic tumors has not been adequately investigated. To assess the full spectrum of Myb's oncogenic capability, a replication-competent retroviral vector (RCAMV) was used to express a full-length protein (C-Myb), an amino-terminally truncated protein (VCC- or delta N-Myb), a carboxyl-terminally truncated protein (T-Myb), or a doubly truncated protein (VCT-Myb) in vivo. These viruses were injected intravenously into 10-day chicken embryos, and the infected chicks were monitored for tumors. Approximately 4 to 8 weeks after hatching, the majority (30 of 39 [77%]) of animals infected with the T-Myb retrovirus (without 214 carboxyl-terminal residues) developed nodular muscle tumors which could be identified by both morphologic and immunohistochemical criteria as fibrosarcomas. Identically appearing tumors could also be found in the kidney of some T-Myb-infected animals. The T-Myb-induced fibrosarcomas expressed the appropriately sized T-Myb protein, contained an unaltered proviral T-myb gene, and showed clonal proviral integration sites. In comparison, no sarcomas were observed in any of the animals infected with the amino-terminally truncated (VCC- and delta N-Myb) or doubly truncated (VCT-Myb) viruses. A loss of carboxyl-terminal but not amino-terminal sequences can thus convert Myb into a potent in vivo transforming protein for nonhematopoietic mesenchymal cells. In comparison, a truncation of either or both ends of the protein can activate Myb into a hematopoietic cell-transforming protein.

Animals↗
PubMed1983

Pausing and termination of human RNA polymerase II transcription at a procaryotic terminator.

Kinetic analyses of runoff transcription in a cell-free eucaryotic transcription system revealed that the bacteriophage lambda 4S RNA terminator caused human RNA polymerase II to pause on the template and partially terminate transcription of transcripts initiated by the adenovirus 2 major late promoter. Analogous to the procaryotic RNA polymerase, the eucaryotic enzyme terminated just beyond the guanine-plus-cytosine-rich region of dyad symmetry in the terminator sequence. These results suggest that the eucaryotic RNA polymerase II may respond to transcription termination sequences similar to those used by the procaryotic enzyme. However, similar templates containing lambda tint or lambda tR1 terminators did not elicit pausing or termination, suggesting that other features, such as sequence specificity, may also be involved.

Bacteriophage lambda↗