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Biomedical subjects

T Ohta

Publications and source records attributed to T Ohta.

At least 1,171 records · Page 65Linked to original sources
PubMed1986

Nucleotide sequence of the pbpA gene and characteristics of the deduced amino acid sequence of penicillin-binding protein 2 of Escherichia coli K12.

We have determined the nucleotide sequence of the pbpA gene encoding penicillin-binding protein (PBP) 2 of Escherichia coli. The coding region for PBP 2 was 1899 base pairs in length and was preceded by a possible promoter sequence and two open reading frames. The primary structure of PBP 2, deduced from the nucleotide sequence, comprised 633 amino acid residues. The relative molecular mass was calculated to be 70867. The deduced sequence agreed with the NH2-terminal sequence of PBP 2 purified from membranes, suggesting that PBP 2 has no signal peptide. The hydropathy profile suggested that the NH2-terminal hydrophobic region (a stretch of 25 non-ionic amino acids) may anchor PBP 2 in the cytoplasmic membrane as an ectoprotein. There were nine homologous segments in the amino acid sequence of PBP 2 when compared with PBP 3 of E. coli. The active-site serine residue of PBP 2 was predicted to be Ser-330. Around this putative active-site serine residue was found the conserved sequence of Ser-Xaa-Xaa-Lys, which has been identified in all of the other E. coli PBPs so far studied (PBPs 1A, 1B, 3, 5 and 6) and class A and class C beta-lactamases. In the higher-molecular-mass PBPs 1A, 1B, 2 and 3, Ser-Xaa-Xaa-Lys-Pro was conserved. In the putative peptidoglycan transpeptidase domain there were six amino acid residues, which are common only in the PBPs of higher molecular mass.

Acyltransferases↗
PubMed1986

Nucleotide sequence and characteristics of the gene for L-lactate dehydrogenase of Thermus caldophilus GK24 and the deduced amino-acid sequence of the enzyme.

The gene for L-lactate dehydrogenase (LDH) (EC 1.1.1.27) of Thermus caldophilus GK24 was cloned in Escherichia coli using synthetic oligonucleotides as hybridization probes. The nucleotide sequence of the cloned DNA was determined. The primary structure of the LDH was deduced from the nucleotide sequence. The deduced amino acid sequence agreed with the NH2-terminal and COOH-terminal sequences previously reported and the determined amino acid sequences of the peptides obtained from trypsin-digested T. caldophilus LDH. The LDH comprised 310 amino acid residues and its molecular mass was determined to be 32,808. On alignment of the whole amino acid sequences, the T. caldophilus LDH showed about 40% identity with the Bacillus stearothermophilus, Lactobacillus casei and dogfish muscle LDHs. The T. caldophilus LDH gene was expressed with the E. coli lac promoter in E. coli, which resulted in the production of the thermophilic LDH. The gene for the T. caldophilus LDH showed more than 40% identity with those for the human and mouse muscle LDHs on alignment of the whole nucleotide sequences. The G + C content of the coding region for the T. caldophilus LDH was 74.1%, which was higher than that of the chromosomal DNA (67.2%). The G + C contents in the first, second and third positions of the codons used were 77.7%, 48.1% and 95.5% respectively. The high G + C content in the third base caused extremely non-random codon usage in the LDH gene. About half (48.7%) the codons in the LDH gene started with G, and hence there were relatively high contents of Val, Ala, Glu and Gly in the LDH. The contents of Pro, Arg, Ala and Gly, which have high G + C contents in their codons, were also high. Rare codons with U or A as the third base were sometimes used to avoid the TCGA sequence, the recognition site for the restriction endonuclease, TaqI. Two TCGA sequences were found only in the sequence of CTCGAG (XhoI site) in the sequenced region of the T. caldophilus DNA. There were three segments with similar sequences in the two 5' non-coding regions, probably the promoter and ribosome-binding regions, of the genes for the T. caldophilus LDH and the Thermus thermophilus 3-isopropylmalate dehydrogenase.

Amino Acid Sequence↗
PubMed1986

Structure of the extra-membranous domain of the beta-subunit of (Na,K)-ATPase revealed by the sequences of its tryptic peptides.

Membrane bound dog kidney (Na,K)-ATPase was digested with trypsin. The peptides that were recovered in the supernatant were purified and sequenced. By comparing these results with the sequence of alpha- and human beta-subunits, the location of each of the peptides could be allotted. Both accessibility to trypsin and the facility of release into the water phase indicated that these peptides were derived from the exposed surface of the intact enzyme. The sequence, GXGXXG, reported in the Torpedo californica beta-subunit [(1986) FEBS Lett. 196, 315-319] was likely a mere coincidence with the sequence of the dinucleotide-binding site, since the last glycine was replaced by proline in the sequence of the dog beta-subunit. A disulfide bridge was found within a peptide derived from the beta-subunit. A possible model for the beta-subunit structure is proposed.

Amino Acid Sequence↗
PubMed1986

Peptidoglycan synthetic activities in membranes of Escherichia coli caused by overproduction of penicillin-binding protein 2 and rodA protein.

Penicillin-binding protein (PBP)-2 and the RodA protein are known to function in determining the rod shape of Escherichia coli cells. Peptidoglycan biosynthetic reactions that required these two proteins were demonstrated in the membrane fraction prepared from an E. coli strain that overproduced both of these two proteins and which lacked PBP-1B activity (the major peptidoglycan synthetase activity in the normal E. coli membranes). The cross-linked peptidoglycan was synthesized from UDP-N-acetylmuramylpentapeptide and UDP-N-acetylglucosamine in the presence of a high concentration of cefmetazole that inhibited all of PBPs except PBP-2. The peptidoglycan was synthesized via a lipid intermediate and showed up to 30% cross-linking. The cross-linking reaction was strongly inhibited by the amidinopenicillin, mecillinam, and by other beta-lactam antibiotics that have a high affinity for PBP-2, but not by beta-lactams that had very low affinity for PBP-2. The formation of peptidoglycan required the presence of high levels of both PBP-2 and the RodA protein in the membranes, but it is unclear which of the two proteins was primarily responsible for the extension of the glycan chains (transglycosylation). However, the sensitivity of the cross-linking reaction to specific beta-lactam antibiotics strongly suggested that it was catalyzed by PBP-2. The transglycosylase activity of the membranes was sensitive to enramycin and vancomycin and was unusual in being stimulated greatly by a high concentration of a chelating agent.

Bacterial Proteins↗
PubMed1986

Molecular cloning and sequence analysis of human Na,K-ATPase beta-subunit.

We have isolated a cDNA clone for the beta-subunit of HeLa cell Na,K-ATPase, containing a 2208-base-pair cDNA insert covering the whole coding region of the beta-subunit. Nucleotide sequence analysis revealed that the amino acid sequence of human Na,K-ATPase exhibited 61% homology with that of Torpedo counterpart (Noguchi et al. (1986) FEBS Lett. in press). A remarkable conservation in the nucleotide sequence of the 3' non-coding region was detected between the human and Torpedo cDNAs. RNA blot hybridization analysis revealed the presence of two mRNA species in HeLa cells. S1 nuclease mapping indicated that they were derived from utilization of two distinct polyadenylation signals in vivo. Total genomic Southern hybridization indicated the existence of only a few, possibly one set of gene encoding the Na,K-ATPase beta-subunit in the human genome.

Amino Acid Sequence↗
PubMed1986

Primary structure of the beta-subunit of Torpedo californica (Na+ + K+)-ATPase deduced from the cDNA sequence.

DNA complementary to the Torpedo californica electroplax mRNA coding for the beta-subunit of (Na+ + K+)-ATPase has been cloned by screening a cDNA library with an oligodeoxyribonucleotide probe. Nucleotide sequence analysis of the cloned cDNA has revealed that this polypeptide consists of 305 amino acid residues (including the initiating methionine). The transmembrane topology and the potential N-glycosylation sites of this polypeptide are discussed.

Amino Acid Sequence↗
PubMed1986

Natural history of intermittent claudication in the Japanese.

The natural history of intermittent claudication (IC) was surveyed in 59 limbs of 44 patients. The mean follow-up period was 3 years (1 to 8.3 years). During the follow-up period, 72.0 per cent of the limbs with a solitary arterial lesion improved or remained unchanged. However, detailed analysis showed that 53.3 per cent of limbs with iliac artery stenosis and 50.0 per cent of those with femoropopliteal artery stenosis worsened, whereas only 18.7 per cent of limbs with iliac artery occlusion and no limbs with femoropopliteal artery occlusion had worsening of symptoms. Of limbs with multiple arterial lesions, 62.5 per cent worsened. Although the natural history of IC is relatively favorable, IC due to a solitary arterial stenosis tends to worsen, whereas IC due to a solitary arterial occlusion will, in more than 80 per cent of cases, improve or remain unchanged. In cases of arterial stenosis, therefore, more careful follow-up, including control of risk factors, is mandatory.

Aged↗
PubMed1986

Antimutagenic effects of 5-fluorouracil and 5-fluorodeoxyuridine on UV-induced mutagenesis in Escherichia coli.

Inhibitors of UV induction of the SOS function were screened. A log phase culture of E. coli PQ37 (sulA::lacZ, rfa, uvrA, Phoc) was irradiated with UV and then immediately subjected to culture for 2 h in a liquid LB medium containing each test compound. Expression of the SOS gene (sulA) was assayed by monitoring the levels of beta-galactosidase. In order to examine the inhibitory effects of test compounds on protein synthesis, the levels of the constitutive alkaline phosphatase were assayed in parallel. The total number of compounds tested was 233, including 44 food and feed additives, 23 naturally occurring compounds and derivatives, 21 antibiotics, 61 pesticides, 33 inorganics and 51 other chemicals. As a result, 5-fluorouracil and 5-fluorodeoxyuridine were found to inhibit considerably the UV induction of the SOS gene without any inhibition of protein synthesis. Mutagenesis induced by UV irradiation was depressed by the addition of either compound at non-toxic concentrations.

Alkaline Phosphatase↗
PubMed1986

Inhibitory effects of flavourings on mutagenesis induced by chemicals in bacteria.

The antimutagenic potential of twenty-five flavourings was tested against the activity of several kinds of chemical mutagens in Escherichia coli and Salmonella typhimurium. Anisaldehyde, ethylvanillin and vanillin showed marked antimutagenic effects on mutagenesis induced by 4-nitroquinoline 1-oxide, furylfuramide (AF-2), captan or methylglyoxal in E. coli WP2s. However, they were not effective against mutations provoked by 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) or 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in S. typhimurium TA98. Despite the decrease in the number of mutants, a remarkable increase was observed in the survival of mutagen-treated WP2s cells after exposure to these flavourings. We assume that these compounds may act as bio-antimutagens by enhancing an error-free recombinational repair system, because this reactivation of survival was strictly dependent on the recA gene function but not on the lexA and uvrA gene functions.

Benzaldehydes↗
PubMed1986

Beta-2 adrenergic receptors are not only for circulating catecholamines in ventricular muscles of carp heart (Cyprinus carpio).

Whether beta-2 adrenergic receptors are only for the circulating catecholamines in isolated ventricular muscles of carp heart was studied. Isoproterenol, epinephrine and norepinephrine had concentration dependent positive inotropic effects. The ED50 values for isoproterenol, epinephrine and norepinephrine were 6.23 +/- 1.9, 87.3 +/- 27.3 and 4500 +/- 580 nM, respectively. Phentolamine did not alter the inotropic effects. Tyramine increases the force of contraction and this action was completely blocked by propranolol and reserpine, but not by atenolol. Norepinephrine levels, in comparison with those of epinephrine, were similar in plasma and higher in ventricular muscles. However, the norepinephrine levels in ventricular muscles of carp heart were markedly lower than those in ventricular muscles of rat heart. These results suggest that ventricular muscles of carp heart contain adrenergic neurons, and that a catecholamine released from the nerve terminals, presumably epinephrine, may stimulate beta-2 adrenergic receptors.

Animals↗
PubMed1986

The active site structure of Na+/K+-transporting ATPase: location of the 5'-(p-fluorosulfonyl)benzoyladenosine binding site and soluble peptides released by trypsin.

When the dog kidney Na+/K+-transporting ATPase (EC 3.6.1.37, formerly EC 3.6.1.3) was labeled with an ATP analogue, 5'-(p-fluorosulfonyl)benzoyladenosine (FSBA), there was a concomitant loss of ATPase activity. The presence of ATP protected the enzyme from both labeling and inactivation. The ATP-sensitive incorporation of FSBA is associated only with modification of the alpha subunit from which two labeled tryptic peptides were purified and sequenced. To establish any regions of the enzyme protruding from the membrane, the native Na+/K+-transporting ATPase from the electric ray, Torpedo californica, was treated with trypsin; and four peptides, which were released into the water phase, were purified and sequenced. A comparison of the peptide sequences with the deduced amino acid sequences of the DNA coding for the alpha subunit of T. californica and sheep kidney reveal the following. (i) FSBA-labeled peptides from the dog kidney enzyme are located in the central hydrophilic domain and show almost complete sequence homology with the same region in the alpha subunit from the electric ray and sheep kidney. Furthermore, the sequence homology of one of the two labeled peptides can be extended to the sarcoplasmic Ca2+-transporting ATPase and B subunit of Escherichia coli K+-transporting ATPase. (ii) Three trypsin-exposed peptides are found in the central hydrophilic domain, and one peptide is in the hydrophilic segment near the C terminus of the alpha subunit. (iii) The active center of Na+/K+-transporting ATPase is likely to be constructed from at least four different stretches in the primary sequence and, irrespective of the different specificity of cations, the various cation transport ATPases that form phosphorylated enzyme appear to have a common structure at the catalytic site for ATP hydrolysis.

Adenosine↗
PubMed1986

Population genetics of an expanding family of mobile genetic elements.

A model of an expanding family of dispersed repetitive DNA was studied. Based on the previous result of the model of duplicative transposition, an approximate solution to give allelism and identify coefficients as functions of time was obtained, and theoretical predictions were verified by Monte Carlo experiments. The results show that, even if the copy number per genome increases very rapidly, allelism and identity coefficients may take a long time to reach equilibrium. The changes of allelism and allelic identity are similar to that of homozygosity at an ordinary single locus, whereas that of nonallelic identity can be much slower, particularly when the copy number per genome is large. Thus, many existing families of highly repetitive sequences may represent nonequilibrium states for nonallelic identity. The present model may be extended to include other evolutionary forces such as gene conversion or the recurrent insertion from normal gene copies.

Alleles↗