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Biomedical subjects

M Kohiyama

Publications and source records attributed to M Kohiyama.

At least 73 records · Page 4Linked to original sources
PubMed1983

Escherichia coli uvrD mutants with thermosensitive DNA-dependent adenosine triphosphatase I (helicase II).

Three mutants producing thermosensitive DNA-dependent Adenosine triphosphatase (ATPase) I were screened from a collection of temperature-sensitive mutants of Escherichia coli K12. ATPase I purified to near homogeneity from one of the mutants (JE11000) possesses both thermosensitive DNA-dependent ATPase and DNA helicase activities. We have shown that ATPase I is encoded by the uvrD gene as first suggested by Oeda et al. (1982): (i) the thermosensitive ATPase I mutation present in JE11040 lies in or very close to the uvrD gene, (ii) ATPase I activity is absent in uvrD210, uvrD156, and uvrD252 mutants. Thus the thermosensitive mutations correspond to new uvrD mutations. However, the mutation present in JE11040 confers neither UV sensitivity nor mutator phenotype at high temperature. Evidence is presented that the mutant ATPase I is stabilized in vivo at 42 degrees C.

Adenosine Triphosphatases↗
PubMed1983

Recognition sites for a membrane-derived DNA binding protein preparation in the E. coli replication origin.

The DNA binding protein B' preparation, isolated from the membrane of E. coli, recognizes two sites, one of which is located in the minimum oriC (35-270 bp) and the other between base pairs 417 and 488. Recognition is only possible when restriction fragments containing these sites are in single-stranded state. At the first site the strand reading 3'OH-5'P in the direction of the E. coli genetic map is recognized, at the second site the 5'P-3'OH strand.

Bacterial Proteins↗
PubMed1982

Purification of penicillin-binding protein 3 from Streptococcus pneumoniae.

Penicillin-binding protein 3 from wild-type Streptococcus pneumoniae has been purified to homogeneity by solubilization with Triton X-100 and successive column chromatography. The penicillin-binding activity during the fractionation procedure was monitored with a rapid filter binding assay using [3H]propionylampicillin and penicillin-binding protein 3 identified after fluorography of dodecyl sulfate gels. The purified protein showed penicillin-sensitive D,D-carboxypeptidase activity.

Bacterial Proteins↗
PubMed1980

A DNA-binding protein specific for the early replicated region of the chromosome obtained from Escherichia coli membrane fractions.

After extensive dialysis of Escherichia coli membranes treated with Triton X-100, three membrane proteins (A, B and B') with an affinity for DNA have been isolated and purified. They bind to either double-stranded or single-stranded DNA. A and B' proteins preferentially attach to DNA even in the presence of poly(uridylic acid). Only protein B' can recognize some base sequence of DNA because pulse-labelled DNA made at the initiation of replication in a synchronized dnaC mutant has been selectively retained by the protein.

Calcium↗
PubMed1979

DNA-dependent ATPases from Escherichia coli K12.

Four DNA-dependent ATPases have been isolated from E. coli extracts. ATPases I and III, both sensitive to NEM, require denatured DNA but differ in their heat sensitivity, elution from DEAE-cellulose, and sedimentation coefficient. ATPases II and IV are both resistant to NEM. ATPase II requires partially denatured DNA, whereas ATPase IV can be stimulated by SS DNA. ATPase I is a DNA-unwinding enzyme; ATPase II may be involved in recombination.

Adenosine Triphosphatases↗
PubMed1978

Purification and characterization of DNA-dependent ATPase II from Escherichia coli.

A new DNA-dependent ATPase was isolated and purified from soluble extracts of Escherichia coli. This enzyme, called ATPase II, has a molecular weight of 86,000 and exists in a monomeric state. It degrades ATP (or dATP) to ADP (or dADP) and Pi in the presence of magnesium and requires a double-stranded polynucleotide as cofactor. A correlation between the efficiency as cofactor and the melting point of the polynucleotide has been found; the lower the melting temperature, the higher the stimulation of ATPase II. The enzyme binds to single-stranded DNA and poly[d(A-T)] copolymer, but not to the double-stranded circular DNA (Form I) of simian virus 40.

Adenosine Triphosphatases↗
PubMed1978

Evidences for the existence of two steps in DNA replication obtained in toluene-treated Escherichia coli.

Toluene-treated Escherichia coli can synthesize DNA in the presence of precursors and ATP [Moses, R.E. & Richardson, C.C. (1970) Proc. Natl Acad. Sci. U.S.A. 67, 674--681]. The replacement of ATP by another NTP or dNTP leads to the premature arrest of the reaction. Residual synthesis in the presence of an NTP or dNTP other than ATP differs from the complete reaction in the presence of ATP because it is less sensitive to nalidixic acid and novobiocin and because its maximal activity can be obtained with lower concentrations of dNTP or shorter times of toluene treatment. However, like the complete reaction, residual synthesis occurs at the replication fork pre-existing in vivo at the time of toluenization, produces short and long pieces of DNA, is inhibited by arabinosyl-adenine triphosphate, azide or mitomycin C, and is dependent on the dnaE, DNAB and dnaG gene products. We conclude from these data that ATP is specifically required for a step in DNA replication which involves the activity of DNA gyrase, the target of nalidixic acid and novobiocin [Higgins, N.P., Peebles, C.L., Sugino, A. & Cozzarelli, N.R. (1978) Proc. Natl Acad. Sci. U.S.A. 75, 1773-1777]. In the absence of DNA gyrase activity, short DNA pieces are formed and sealed but only a limited amount of the chromosome can be replicated (residual synthesis). In the presence of DNA gyrase activity, DNA synthesis can occur on a longer portion of the chromosome (complete synthesis).

DNA Replication↗
PubMed1977

Escherichia coli membrane proteins with an affinity for deoxyribonucleic acid.

From the membrane fraction of Escherichia coli K-12 strain, four protein fractions (peaks I, IIa, IIb, and III) which have affinity for deoxyribonucleic acid (DNA) have been isolated. The molecular weights of these proteins are between 12,000 and 8,000. Only the peak III fraction contains a protein that binds preferentially to single-stranded DNA, whereas the others contain proteins that bind also to double-stranded DNA. The binding activity of the peak IIb protein is inhibited in the presence of polyuridylic acid. Peak I and peak IIa protein fractions behave like hydrophobic proteins.

Bacterial Proteins↗
PubMed1976

Purification and characterization of a DNA-dependent ATPase from Escherichia coli.

A DNA-dependent ATPase has been isolated and purified from an Escherichia coli cell-free extract. The ATPase has the following characteristics: preferential dependence on single-stranded DNA, specificity for ATP hydrolysis, Km value of 1.4 X 10-4 M for ATP, and molecular weight of approximately 69,000. The ATPase can be shown to bind to single stranded DNA. The resemblance between this ATPase and that isolated from vaccinia cores is discussed.

Adenosine Triphosphatases↗