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Biomedical subjects

H Aiba

Publications and source records attributed to H Aiba.

At least 127 records · Page 7Linked to original sources
PubMed1985

Negative regulation of adenylate cyclase gene (cya) expression by cyclic AMP-cyclic AMP receptor protein in Escherichia coli: studies with cya-lac protein and operon fusion plasmids.

We constructed cya-lac protein and operon fusion plasmids in vitro. The effect of cyclic AMP (cAMP) on cya expression was examined by measuring the synthesis of beta-galactosidase in Escherichia coli cells containing fused plasmids. In the cya-lacZ fused protein system, cya expression was strongly repressed by exogenous cAMP. Functional cAMP receptor protein (CRP) was necessary for this effect. On the other hand, in a tet-lacZ fused protein as a control system, tet expression was not affected by cAMP. The inhibition of cya expression by cAMP was also observed in the cya-lac fused operon system, although it was necessary to increase the amount of cAMP or CRP in the cells to detect the effect. The results indicate that cAMP-CRP is a negative regulator of cya expression at the level of transcription.

Adenylyl Cyclases↗
PubMed1984

The complete nucleotide sequence of the adenylate cyclase gene of Escherichia coli.

The complete nucleotide sequence of the cya gene from E. coli was determined. The gene encodes a polypeptide consisting of 848 amino acid residues with a calculated molecular weight of 97,542. The deduced protein structure reveals that cyclase is comprised of two domains, an amino-terminal region exhibiting catalytic activity and a carboxy-terminal region possibly carrying regulatory function. The frequent appearance of rare codons in the beginning of the gene as well as the sequence duplication in the promoter-initiator region suggest possible regulation(s) at the translational level. An unknown gene (cyaX) which seems to code for a very hydrophobic protein was found following the cya gene. Sequence analysis suggests that the cyax is a part of the cya operon.

Adenylyl Cyclases↗
PubMed1983

Cloning and promoter analysis of the Escherichia coli adenylate cyclase gene.

The gene for adenylate cyclase of E. coli has been cloned in the plasmid pBR322. The Cya- strain transformed with the isolated plasmids produces significant amounts of adenylate cyclase and cAMP. Some of the Cya+ plasmids were shown to direct the synthesis of a 85,000 dalton polypeptide in a cell-free system. The direction of transcription and the location of the cya promoter including the transcriptional start site were determined by an S1 digestion method. DNA sequence around the promoter region indicates that a putative coding region for adenylate cyclase begins at +233. The 233 bp leader region could encode a potential small polypeptide containing 30 amino acids. Two probable CRP binding sites were found in the leader region, suggesting a negative control at the transcriptional level by CRP-cAMP.

Adenylyl Cyclases↗
PubMed1983

Changes of enzyme activities recognized in lymphocytes from patients with carcinoma of the gastrointestinal tract.

Adenosine triphosphatase (ATPase) activity and acid phosphatase activity in lymphocytes from patients with carcinoma of the gastrointestinal tract were determined in order to investigate whether or not changes in these enzyme activities has any relation to the immune reactivity of carcinoma-bearing patients. In patients with a performance status of more than 60%, the mean value of the total ATPase activity in lymphocytes differed little from that in controls, but the mean value of the oligomycin-sensitive ATPase activity decreased as compared to that in the controls. On the other hand, the mean values of the activities of both free and total acid phosphatase in lymphocytes increased as compared to those in controls. The mean values of the activities of both ATPase and acid phosphatase in lymphocytes from patients whose performance status was less than 50% decreased as compared to those from controls and patients whose performance status was more than 60%. The change of the activities of both ATPase and acid phosphatase in lymphocytes has relation to that of the immunological parameters of the patients with carcinoma of the gastrointestinal tract. These results indicate that both ATPase and acid phosphatase in lymphocytes may play an important role in the immune mechanism.

Acid Phosphatase↗
PubMed1983

Autoregulation of the Escherichia coli crp gene: CRP is a transcriptional repressor for its own gene.

The restriction fragments carrying the region preceding the Escherichia coli crp structural gene were transcribed. The 5' end of the crp mRNA was determined by RNAase partial digestion and S1 digestion methods. Thus the crp gene has been shown to possess a 167 bp leader. CRP-cAMP specifically prevents the crp transcription. In other words, the crp gene is regulated autogenously. DNAase foot-printing studies indicated that CRP-cAMP binds to the crp gene at positions +26 to +67. This region exhibits a striking sequence homology to the CRP-binding sites in other genes. CRP and RNA polymerase bind to the crp regulatory region simultaneously. These results suggest a different mechanism for transcriptional repression of the crp gene by CRP-cAMP from that of a typical operator-repressor model.

Base Sequence↗
PubMed1982

Molecular cloning and nucleotide sequencing of the gene for E. coli cAMP receptor protein.

The crp gene of E. coli, which codes for cAMP receptor protein (CRP), has been cloned in the plasmid pBR322 on the basis of a genetic complementation. One of the recombinant plasmids, pHA1, was shown to direct the synthesis of CRP in a cell-free system. The location of the crp gene was determined by constructing subclones carrying various portions of pHA1. The nucleotide sequence of the crp gene has been determined. The coding region consists of 627 base pairs (bp), which specify a protein of 209 amino acids. The predicted amino acid sequence from the DNA sequence is consistent with the amino acid sequence partially known and the amino acid composition of CRP. After the coding region, there is a G-C rich inverted repeat sequence followed by a run of Ts, which could be a terminator of the crp gene. A possible promoter sequence was found about 180 bp upstream from the initiation codon and was shown to act as a promoter in vitro and in vivo. There are two dyad symmetry regions in a 167 bp leader sequence.

Amino Acid Sequence↗
PubMed1982

The structure of tandem regulatory regions in the deo operon of Escherichia coli K12.

The transcription initiation sites of the deo operon of Escherichia coli K12 have been determined in vitro and in vivo. Initiation of transcription occurs at two, tandemly arranged, homologous regions which are located 600 base pairs apart from each other. Evidence for a novel regulation mechanism of deo gene expression involving the deoR repressor is presented.

Journal Article↗
PubMed1981

Evidence for two functional gal promoters in intact Escherichia coli cells.

We have used an S1 mapping assay to demonstrate that the mRNA transcripts of the Escherichia coli galactose operon found in intact E. coli cells with a defect in adenylate cyclase or the cyclic AMP receptor protein contain at their 5' end about five nucleotides more than the gal mRNA molecules made in wild type cells. The same difference between gal RNA synthesized in vitro in the absence of cyclic AMP or cyclic AMP receptor protein and gal RNA made in the presence of these factors is detected by this assay. Our results strongly suggest that the same two overlapping promoters, which we previously identified by in vitro transcription of gal DNA fragments, also control the expression of the galactose operon in intact cells. The intracellular levels of cyclic AMP determine which promoter is utilized.

DNA, Bacterial↗
PubMed1981

Isolation and characterization of the amino and carboxyl proximal fragments of the adenosine cyclic 3' ,5'-phosphate receptor protein of Escherichia coli.

The cyclic AMP receptor protein (CRP) is a positive and negative regulatory protein for gene expression in Escherichia coli. The protein has been cleaved proteolytically to determine the relation between CRP structure and function. In the presence of sodium dodecyl sulfate (NaDodSO4), chymotrypsin dissects CRP into two stable fragments of molecular weight 9500 (9.5K) and 13 000 (13K). After removal of NaDodSO4, the two fragments are resolved by Bio-Rex 70 chromatography in 6 M urea. Analyses of the terminal amino acids released from each fragment and cyanogen bromide cleavage products indicate that the 9.5K fragment is amino proximal in CRP while the 13K fragment is carboxyl proximal. Notable features of amino acid composition are the relatively high amount of arginine and methionine in the 13K fragment and the retention in the 9.5K fragment of the two tryptophans present in the CRP subunit. Following isoelectric focusing in 8 M urea, the 9.5K fragment, 22.5K CRP, and 13K fragment migrate to pH 5.5, 8.3, and 10.3, respectively. While CRP is a cAMP-stimulated DNA binding protein, the 13K fragment binds to DNA in the presence and absence of cAMP. The 9.5K fragment associates to form dimers and decamers. These data are consonant with a model in which the DNA binding domain is present in the carboxyl proximal region of CRP while the amino proximal region contains the subunit-subunit interaction sites and much of the cAMP binding domain.

Amino Acids↗
PubMed1980

Photoaffinity labeling of the adenosine cyclic 3',5'-monophosphate receptor protein of Escherichia coli with 8-azidoadenosine 3',5'-monophosphate.

Photoaffinity labeling of the cAMP receptor protein (CRP) of Escherichia coli with 8-azidoadenosine 3',5'-monophosphate (8-N3cAMP) has been demonstrated. 8-N3cAMP is able to support the binding of (3H)d(I-C)n by CRP, indicating that it is a functional cAMP analogue. Following irradiation at 254 nm, (32P)-8-N3cAMP is photocross-linked to CRP. Photolabeling of CRP by (32P)-8-N3cAMP is inhibited by cAMP but not by 5'AMP. The data indicate that (32P)-8-N3cAMP is covalently incorporated following binding at the cAMP binding site of CRP. The (32P)-8-N3cAMP-CRP digested with chymotrypsin was analyzed by NaDodSO4-polyacrylamide gel electrophoresis. Of the incorporated label, one-third remains associated with the amino-proximal alpha core region of CRP [Eilen, E., Pampeno, C., & Krakow, J.S. (1978) Biochemistry 17, 2469] which contains the cAMP binding domain; the remaining two-thirds of the label associated with the beta region are digested. Limited proteolysis of the (32P)-8-N3cAMP-CRP by chymotrypsin in the presence of NaDodSO4 shows the radioactivity to be distributed between the molecular weight 9500 (amino-proximal) and 13,000 (carboxyl-proximal) fragments produced. These results suggest that a part of the carboxyl-proximal region is folded over and close enough to the cAMP binding site to be cross-linked by the photoactivated (32P)-8-N3cAMP bound at the cAMP binding site.

Affinity Labels↗
PubMed1979

Subunits of RNA polymerase in function and structure. 7. Structure of premature core enzyme.

The structure of premature core enzyme, an obligatory intermediate in both in vivo and in vitro assembly of Escherichia coli DNA-dependent RNA polymerase, was compared with that of native core enzyme. Though this assembled but inactive form of core enzyme harbors the gross conformation similar to that of native enzyme, minor and presumably local differences exist, which were identified by near-ultraviolet circular dichroism spectra, tritium-hydrogen exchange rate, protease sensitivity, intersubunit cross-linking rate by bifunctional reagents, sedimentation behavior, and elution profile from phosphocellulose. Taken together these results indicate that the core enzyme subunits are loosely associated in the premature core. The temperature-dependent maturation is required for the core subunits to be tightly associated, leading to the formation of structurally stable and functionally active RNA polymerase.

Circular Dichroism↗