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At least 721 records · Page 40Linked to original sources
PubMed1996

The Tetrahymena chaperonin subunit CCT eta gene is coexpressed with CCT gamma gene during cilia biogenesis and cell sexual reproduction.

We report here the cloning and the characterization of the T. pyriformis CCT eta gene (TpCCT eta) and also a partial sequence of the corresponding T. thermophila gene (TtCCT eta). The TpCCt eta gene encodes a protein sharing a 60.3% identity with the mouse CCT eta. We have studied the expression of these genes in Tetrahymena exponentially growing cells, cells regenerating their cilia for different periods and during different stages of the cell sexual reproduction. These genes have similar patterns of expression to those of the previously identified TpCCt gamma gene. Indeed, the Tetrahymena CCT eta and CCT gamma genes are up-regulated at 60-120 min of cilia recovery, and in conjugation when vegetative growth was resumed and cell division took place. Our results seem to indicate that both CCT subunits play an important role in the biogenesis of the newly synthesized cilia of Tetrahymena and during its cell division.

Amino Acid Sequence↗
PubMedDate not supplied

Methoxylation of 3beta,7alpha-dihydroxychol-5-en-24-oic acid, a key intermediate of chenodeoxycholic acid biogenesis, compared with that of its 7beta-epimer.

The conventional methods of gas liquid chromatography or mass spectrometry failed to be useful for the identification of the biliary 3beta,7alpha-dihydroxychol-5-en-24-oic acid, a key intermediate of chenodeoxycholic acid biogenesis. It has been preliminarily reported that this acid in human bile was successfully identified by gas chromatography-mass spectrometry, after the methoxylation of its allyl alcohol group. Physical as well as spectral properties of the methoxylation products derived from the acid were reported, compared with those from its 7beta-epimer.

Chemical Phenomena↗
PubMedDate not supplied

Methoxylation of methyl 3alpha,7alpha-dihydroxychol-4-en-24-oate and its 3beta-epimer. A contribution to chenodeoxycholic acid biogenesis.

By the conventional methods of gas liquid chromatography (GLC) as well as mass spectrometry, 3beta,7alpha-dihydroxychol-5-en-24-oic acid (delta5-acid), a key intermediate of chenodeoxycholic acid biogenesis and its metabolic by-product, 3alpha,7alpha-dihydroxychol-4-en-24-oic acid (delta4-acid) have not yet been identified as such probably due to thermal decomposition. However, taking advantage of the observation that they are readily methoxylated in methanol containing a trace of acids, their individual methoxy-compounds were easily prepared and proved to be useful for their identification, even though they are present in minimal amounts as was the case with the human or hen bile. The present paper reported physical as well as spectral properties of the methoxy-compounds derived from methyl 3alpha,7alpha-dihydroxychol-4-en-24-oate, compared with those of its 3beta-epimer.

Chemical Phenomena↗
PubMed1991

A prominent antigenic surface polypeptide involved in the biogenesis and function of the vaccinia virus envelope.

Polypeptides of the vaccinia virus envelope exposed on the surface were identified by means of sulfo-N-hydroxysuccinimidobiotin as a surface tag. Among surface expressed polypeptides is the 35-kDa antigen, previously designated Ag35. Both monoclonal (mAb) and monospecific affinity pure antibodies directed against Ag35 neutralized vaccinia infectiousness, indicating that this prominent surface antigen has a function during early virus-host cell interactions. The binding of several monoclonal antibodies to various regions of Ag35 was tested by reacting CNBr fragments, derived from the polypeptide, employing Western blotting. All mAbs tested reacted with the same region of Ag35. Estimation of the molecular weights (MW), based on migration of the CNBr peptides in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, revealed that those partial digestion products which contained a proline-rich 99 amino acid limit digest fragment were present at a position approximately 12.5 kDa larger than that predicted from the DNA sequence. By contrast, partial and limit digest products lacking the proline-rich fragment migrated to the MW position expected from the length of the DNA sequence. This observation demonstrates that departure from a predicted 22.3 kDa to an anomalous MW of Ag35 is conferred by the proline-rich peptide. The surface location of Ag35 was confirmed by immune electron microscopy. In a competition test the binding specificity of mAb and affinity-purified antibodies at the surface of virions could be demonstrated. Evidence for an association of Ag35 with the virus envelope at various stages during biogenesis of vaccinia was obtained by immune electron microscopy of whole mounts and thin sections. Presence of Ag35 as an early component of immature and mature virions, probably residing in the bilayer membrane structure was detected. A distinction can, therefore, be made between Ag35 and several other vaccinia envelope polypeptides which are synthesized as late functions and added during late stages of envelope assembly.

Animals↗
PubMed1983

Genetics and biogenesis of cytochrome b.

We have reviewed here the genetic methods used for isolating and manipulating nuclear and mitochondrial mutants of bakers' yeast that affect the function and biogenesis of complex III of the mitochondrial respiratory chain. All the methods have been used with success in the past, and it is hoped that this compilation will aid biochemists in using these techniques to study electron transfer.

Base Composition↗
PubMed1979

Cilia regeneration in starved tetrahymena: an inducible system for studying gene expression and organelle biogenesis.

Deciliated starved Tetrahymena recover motility with kinetics similar to those of growing cells and, like growing cells, require RNA and protein synthesis for regeneration. Comparisons of polysome profiles and electrophoretic analyses of newly synthesized proteins indicate, however, that the basal level of protein synthesis in starved cells is markedly lower than that in growing cells. This difference allows demonstration of changes in protein synthesis following deciliation of starved cells which cannot be detected (if they occur at all) in growing cells. Deciliation of starved cells induces a specific and orderly program of protein synthesis. The synthesis of an 80,000 dalton protein (deciliation-induced protein, DIP) begins shortly after deciliation, comprises 15% of the protein synthesized from 20-60 min, and declines around 60 min after deciliation, shortly after most cells have begun to regenerate cilia. The synthesis of a 55,000 dalton protein is also induced during regeneration and has been identified as tubulin using a well characterized antibody made to ciliary tubulin. Tubulin synthesis is undetectable during the first hour after deciliation even though 60-80% of the cells regain mobility and regenerate short but clearly visible cilia. Tubulin synthesis begins 60 min after deciliation and continues for 2 hr. At its peak, tubulin comprises 7-8% of the protein synthesized. The results of actinomycin D addition at different times after deciliation suggest that RNA required for DIP synthesis is synthesized early (0-30 min), while RNA required for tubulin is synthesized later and over a longer period (30-90 min). Thus deciliation of starved cells, an event occurring at the cell periphery, initiates a well defined and reproducible series of events culminating in cilia formation. This system should be useful in elucidating the molecular mechanisms regulating gene expression and organelle biogenesis in Tetrahymena.

Animals↗
PubMed1984

Biogenesis of epithelial cell polarity: intracellular sorting and vectorial exocytosis of an apical plasma membrane glycoprotein.

To study the biogenetic pathway of influenza hemagglutinin (HA), a model apical glycoprotein, in polarized epithelial MDCK cells, anti-HA antibodies were added to the basolateral surface during influenza infection. In monolayers grown on collagen gels influenza and VSV plaque development was blocked only when the antibodies were added to the respective budding surface. Addition of anti-HA antibodies to the basal medium of monolayers grown on nitrocellulose filter chambers neither resulted in HA-coupled transport of antibody nor inhibited HA migration to the apical surface. These results indicate that the bulk of HA is vectorially inserted into the apical surface of MDCK cells by polarized exocytosis. Other apical proteins in epithelia may use a similar mechanism during biogenesis.

Animals↗
PubMed1987

Biogenesis of E. coli Pap pili: papH, a minor pilin subunit involved in cell anchoring and length modulation.

The biogenesis of Escherichia coli Pap pili, encoded by the pap gene cluster, was studied. A novel gene, papH, was identified and found to encode a weakly expressed pilin-like protein. PapH was dispensable for digalactoside-specific binding and for formation of Pap pili. However, in papH deletion mutants 50%-70% of total pilus antigen was found free of the cells. We present evidence showing coregulation of papH and the adjacent gene, papA, which encodes the major pilin subunit. A decrease in the PapA to PapH ratio resulted in a large fraction of cells producing shortened pili, whereas overproduction of PapA relative to PapH resulted in cells with lengthened pili. The data show that PapH has roles in anchoring the pilus to the cell and in modulating pilus length.

Amino Acid Sequence↗
PubMed1991

PAS1, a yeast gene required for peroxisome biogenesis, encodes a member of a novel family of putative ATPases.

PAS genes are required for peroxisome biogenesis in the yeast S. cerevisiae. Here we describe the cloning, sequencing, and characterization of the PAS1 gene. Its gene product, Pas1p, has been identified as a rather hydrophilic 117 kd polypeptide. The predicted Pas1p sequence contains two putative ATP-binding sites and reveals a structural relationship to three other groups of proteins associated with different biological processes such as vesicle-mediated protein transport (NSF and Sec18p), control of cell cycle (Cdc48p, VCP, and p97-ATPase), and modulation of gene expression of the human immunodeficiency virus (TBP-1). The proteins share a highly conserved domain of about 185 amino acids including a consensus sequence for ATP binding. We suggest that these proteins are members of a novel family of putative ATPases and may be descendants of one common ancestor.

Adenosine Triphosphatases↗
PubMed1983

Microscale purification of proteins by line immunoelectrophoresis: application of the technique in protein biogenesis studies.

A small-scale version of line immunoelectrophoresis in combination with immunoprecipitate excision is described as a rapid and convenient technique to purify proteins on a micro scale in biogenesis studies. In the purification and to result in a higher state of purity than an isolation procedure using protein A-Sepharose. Since the method furthermore allows a simultaneous purification of several different protein antigens from the same sample, it may be of interest as an alternative method to other procedures in the purification of proteins on a micro scale.

Animals↗
PubMed1993

Ultrastructural aspects of the biogenesis of peroxisomes in rat liver.

A model summarizing our current concepts on the ultrastructural basis of the biogenesis of peroxisomes is presented. Accordingly, the initial stage of de novo build-up of peroxisomes is characterized by the formation of myelin-like figures and membranous attachments onto the surface of pre-existing peroxisomes. Such membranous structures may provide the appropriate lipid environment for the incorporation of peroxisomal membrane proteins and subsequently become the preferential sites for import of newly synthesized matrix proteins. After the import the membranous structures develop into small peroxisomes which may remain attached briefly to the larger particles but eventually separate to become new peroxisomes. Whereas some matrix proteins such as catalase are distributed in all newly formed peroxisomes, other ones like urate oxidase and D-amino acid oxidase are compartmentalized only in some of them, giving rise to heterogeneity of peroxisomes.

Animals↗
PubMed1993

Adrenoleukodystrophy gene: unexpected homology to a protein involved in peroxisome biogenesis.

Adrenoleukodystrophy (ALD) is an X-linked peroxisomal disorder characterized by a progressive demyelination of the central nervous system and adrenal insufficiency. Clinical phenotypes of different severity are frequently observed within the same kindred. ALD is characterized biochemically by the accumulation of very-long-chain fatty acids (VLCFA) due to an impairment in the beta-oxidation of these fatty acids in peroxisome. From the observation that oxidation of VLCFA-CoA is normal in fibroblasts from patients with ALD, it was concluded that the gene coding for VLCFA-CoA synthetase was a candidate gene for ALD. Using positional cloning strategies, we have identified a gene which was found partially deleted in 7% of 85 independent patients with ALD. The predicted protein (ALDP) sequence shows significant homology to the 70-kDa peroxisomal membrane protein which is involved in peroxisome biogenesis and belongs to the 'ATP binding' superfamily of transporters. ALDP thus encodes a putative peroxisomal transporter molecule which may be involved in the import or anchoring of VLCFA-CoA synthetase.

Adrenoleukodystrophy↗
PubMed1993

The ClpE protein involved in biogenesis of the CS31A capsule-like antigen is a member of a periplasmic chaperone family in gram-negative bacteria.

The putative chaperone-like protein ClpE, required for biogenesis of the Escherichia coli capsule-like antigen CS31A, was compared with ten known periplasmic chaperones from E. coli, Klebsiella pneumoniae, Bordetella pertussis, Haemophilus influenzae and Yersinia pestis. The amino acid sequence alignment was superimposed onto the three-dimensional structure of the PapD chaperone of uropathogenic E. coli, and amino acid residues involved in maintaining the structure integrity of the suggested binding site were found identical in most of the 11 chaperones. Construction of a phylogenetic tree to investigate the relationship within the chaperone family has revealed interesting degrees of relatedness between the different proteins.

Amino Acid Sequence↗
PubMed1993

Biogenesis and regulation of the Vibrio cholerae toxin-coregulated pilus: analogies to other virulence factor secretory systems.

Biogenesis of the toxin-coregulated pilus (TCP) of Vibrio cholerae 01 is essential for successful bacterial colonization of the small intestine. Pilus assembly requires the products of at least seven genes located on the chromosome adjacent to the pilin-encoding gene, tcpA. Previously reported TnphoA insertions in the TCP-assembly-deficient V. cholerae strains, KP2.21 and KP4.2, were isolated from the chromosome for further analysis. Nucleotide sequencing of the tcpE::phoA and tcpF::phoA fusions and corresponding clones of the region containing the intact genes revealed the presence of two open reading frames (ORFs) of 340 and 338 amino acids, designated TcpE and TcpF, respectively. The partial sequence of an ORF downstream from the TcpF coding sequence was determined to correspond to the global virulence regulator, ToxT. Proteins corresponding to the observed ORFs were visualized with the T7 promoter/RNA polymerase expression system. Computer-generated alignment algorithms predict that a homology exists between TcpE and the Klebsiella pneumoniae pullulanase secretion proteins PulD and PulF, the Xanthomonas campestris extracellular enzyme secretion factor XpsF, the Bacillus subtilis DNA competence protein ComG-ORF2, and the Yersinia enterocolitica Yop secretion determinant YscC. These observations provide a model to investigate further the relationship between the secretion mechanisms utilized by these seemingly diverse virulence determinants. Additionally, an extreme C-terminal segment of TcpE shows striking homology to the transmembrane segment of the eukaryotic integrin beta-1 chain, which could imply a role for TcpE in not only TCP secretion, but also host cell interaction.

Amino Acid Sequence↗
PubMed1995

Chromosomal localization of mitochondrial transcription factor A (TCF6), single-stranded DNA-binding protein (SSBP), and endonuclease G (ENDOG), three human housekeeping genes involved in mitochondrial biogenesis.

By using a PCR-based screening of a somatic cell hybrid panel and FISH, we have assigned the loci of mitochondrial single-stranded DNA-binding protein (SSBP), mitochondrial transcription factor A (TCF6), and mitochondrial endonuclease G (ENDOG) genes to human chromosomes 7q34, 10q21, and 9q34.1, respectively. The products of these three genes are involved in fundamental aspects of mitochondrial biogenesis, such as replication and transcription of the mitochondrial genome. The chromosomal localization of these genes is important to testing whether the corresponding proteins may play a role in the etiopathogenesis of human disorders associated with qualitative or quantitative abnormalities of mitochondrial DNA.

Chromosome Mapping↗
PubMed1992

Biogenesis of storage granules and vesicles.

The production of storage granules and vesicles that undergo regulated exocytosis occurs via biosynthetic and endocytotic pathways, respectively. Prominent in the formation of secretory granules in the Golgi apparatus is selective protein aggregation, which may account for the biogenesis of multiple granules in a single cell. New cDNA transfection and immunolocalization studies have helped to further refine our understanding of the relationship between the formation of regulated secretory vesicles and the early stages of the endocytotic pathway. Recent insights into the targeting of membrane proteins to these organelles have implicated both specific sorting signals and protein-protein aggregation.

Animals↗
PubMed1993

Biogenesis of constitutive secretory vesicles, secretory granules and synaptic vesicles.

The formation of constitutive secretory vesicles and secretory granules from the trans-Golgi network is inhibited by brefeldin A, suggesting a role for ADP ribosylation factor and other coat proteins in the budding process, and is regulated by multiple heterotrimeric G proteins. Membrane proteins are sorted to secretory granules through signals in their cytoplasmic domains and, like secretory proteins, by aggregation of their lumenal domains. Synaptic vesicle membrane proteins undergo exocytotic-endocytotic recycling before synapse formation, consistent with the proposed biogenesis of synaptic vesicles from early endosomes.

Biopolymers↗
PubMed1991

Testicular function in uremic rats: in vivo assessment of testosterone biogenesis.

The mechanism of testosterone (T) production defect in uremic rats has not yet been clearly defined and hypothalamo-hypophyseal impairment as well as primary testicular dysfunction have been suggested. In 42 rats followed monthly after subtotal nephrectomy up to 7.1 +/- 0.3 months, we observed a progressive significant decline of T and androstenedione (A) compared to control rats. Two months before the terminal phase of chronic renal failure (CRF), T/A ratio abruptly declined. T and its precursors on the 4-ene pathway, A, progesterone (P) and 17-hydroxyprogesterone were evaluated in pampiniform plexus testicular vein (PPTV) and in peripheral blood (PV) in end stage uremic rats (blood urea greater than 30 mmol/l, creatinine clearance less than 0.5 ml/min). Under basal conditions, all steroids but peripheral P were significantly lower in uremic rats than in controls as well as T/P and A/P ratios. After human chorionic gonadotropin (hCG) stimulation, T concentration in PV and PPTV remained highly significantly lower than in controls whereas T precursor concentrations were partially corrected by hCG administration. T/P ratio remained lower than in controls whereas A/P ratio was not significantly lower than in controls. Those data show a decline in all the steps of T biogenesis in uremic rats in basal conditions. The defect in 17 beta-hydroxysteroid dehydrogenase evidenced by T/A decrease at the end stage of CRF seems of primary testicular origin as it is not corrected by hCG administration as shown by T/P and A/P ratios in PPTV and in PV.

17-alpha-Hydroxyprogesterone↗