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Biomedical subjects

U Maitra

Publications and source records attributed to U Maitra.

At least 73 records · Page 4Linked to original sources
PubMed1974

Thiostrepton inhibition of initiation factor 1 activity in polypeptide chain initiation in Escherichia coli.

Thiostrepton, a peptide antibiotic, inhibits the GTP-dependent 70S initiation complex formation (as measured by binding of fMet-tRNA to ribosomes and concomitant hydrolysis of GTP) only when initiation factor 1 is present to permit catalytic recycling of initiation factor 2 in the initiation reaction. When initiation factor 1 is absent, the binding of fMet-tRNA and GTP hydrolysis occur stoichiometrically with respect to initiation factor 2, and thiostrepton has no effect on either reaction under these conditions. Detailed analysis of this inhibition process shows that thiostrepton prevents catalytic recycling of initiation factor 2 by blocking the action of initiation factor 1, which is required for the dissociation of initiation factor 2 from the 70S initiation complex. This dissociation is necessary for the catalytic reutilization of initiation factor 2 in the initiation reaction. The antibiotic does not directly inhibit GTP hydrolysis per se in initiation. The inhibition of fMet-tRNA binding to ribosomes by thiostrepton is also dependent on the concentration of GTP; the inhibition is most pronounced at low concentrations of GTP, but at a high molar ratio of GTP to thiostrepton, the inhibition is completely abolished.

Anti-Bacterial Agents↗
PubMed1972

Initiation, release, and reinitiation of RNA chains by bacteriophage-T3-induced polymerase from T3 DNA templates (E. coli-guanosine triphosphate terminus-purified polymerase).

Bacteriophage T3-induced RNA polymerase, upon copying its specific template, native T3 DNA, initiates RNA chains only with GTP. Denaturation of the DNA results in loss of template specificity for the polymerase. With denatured T3 DNA as template, T3 polymerase initiates RNA chains with both ATP and GTP, and the average length of the resulting RNA chains is markedly reduced. Studies of the polymerase reaction with native T3 DNA in vitro show that T3 polymerase is able to terminate RNA synthesis with the release of RNA chains from the template DNA. Polymerase is also released in the process and, acting catalytically, reinitiates new RNA chains. Many moles of RNA chains are thus formed per mole of polymerase added to the reaction mixture.

Adenosine Triphosphate↗
PubMed1972

Release of polypeptide chain initiation factor IF-2 during initiation complex formation.

Polypeptide chain initiation factor IF-2 binds to 30S ribosomal subunits. This binding is enhanced by IF-1 and IF-3. During GTP-dependent formation of a 70S initiation complex, IF-2 is released from the ribosome. During 70S initiation complex formation dependent on the methylene analogue of GTP, GMPPCH(2)P, IF-2 is not released, but remains bound to the 70S ribosome. This result suggests that IF-2 release requires GTP hydrolysis. In agreement with this presumed requirement, IF-2 functions catalytically with GTP, but stoichiometrically with GMPPCH(2)P, in bringing about 70S initiation complex formation.

Centrifugation, Density Gradient↗