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Biomedical subjects

F Lipmann

Publications and source records attributed to F Lipmann.

At least 55 records · Page 3Linked to original sources
PubMed1973

Identification of the synthesis of guanosine tetraphosphate (MS I) as insertion of a pyrophosphoryl group into the 3'-position in guanosine 5'-diphosphate.

The phosphate transfer system of Haseltine et al., consisting of a ribosomal wash obtained from a stringent strain of Escherichia coli, washed ribosomes, GTP, and ATP, was used to prepare large quantities of guanosine tetra- and pentaphosphates, the magic spot compounds MS I and MS II of Cashel and Gallant. In our hands, the Haseltine et al. system yielded predominantly guanosine tetraphosphate, ppGpp. This system was used exclusively in the described experiments, with ATP labeled with (32)P in the beta- and gamma-positions as donor. The beta-label was found to produce a ppGp⃰p and the gamma-label a ppGpp⃰. Furthermore, [(3)H]GDP + [gamma-(32)P]ATP yielded ppGpp in a (3)H:(32)P ratio of 1:1. The results indicate a transfer of the terminal pyrophosphoryl group of ATP as a unit. The position of the transferred pyrophosphoryl was assayed for by preparation of pGp⃰ from ppGp⃰p with Zn(++)-activated inorganic pyrophosphatase from yeast. The pGp⃰ was then assayed with 3'-nucleotidase, which liberated practically all the labeled phosphate. This result indicate that the phosphate transfer from ATP to GDP yields guanosine 5'-diphosphate-3'-diphosphate.

Adenosine Triphosphate↗
PubMed1973

Nonribosomal synthesis of guanosine 5',3'-polyphosphates by the ribosomal wash of stringent Escherichia coli.

A factor in the ribosomal wash of stringent strains of E. coli was identified by Haseltine et al. as a complement to the ribosomal system for the synthesis of the magic spot compounds of Cashel and Gallant. This factor has been found, in the absence of ribosomes, to catalyze the enzymatic pyrophosphoryl transfer from ATP to GTP or GTP in the formation of magic spot I and magic spot II, the guanosine tetra- and pentaphosphates (ppGpp and pppGpp), respectively. The enzyme, which normally requires the presence of the ribosome-tRNA-mRNA complex for activity, catalyzes a very slow synthesis that is stimulated tenfold by 20% methanol. The temperature optimum of the methanol-stimulated system is 25-30 degrees and activity is drastically depressed at 37 degrees , presumably by inactivation. Catalysis is linear with enzyme concentration and with time for the first 3 hr; during this period 25% of the added GTP is converted. The nonribosomal system is distinguished from the ribosomal system by having a lower Mg(++) and a higher NH(4) (+) optimum. The two systems differ in their response to antibiotics: thiostrepton strongly inhibits the ribosomal system but has no effect on the nonribosomal system.

Ammonium Chloride↗
PubMed1971

Interaction of eukaryote initiator methionyl-tRNA with the eukaryote equivalent of bacterial elongation factor T and guanosine triphosphate.

The initiator tRNA, methionyl-tRNA(i) (Met), of yeast and wheat germ forms relatively unstable ternary complexes with their corresponding elongation factors T and GTP. Such complexes can be demonstrated only with fast separation techniques such as Sephadex G-50 and Millipore filtration, but not with the slow Sephadex G-100 method, although both techniques yield stable ternary complexes with all other aminoacyl-tRNAs, including the internal Met-tRNA(m) (Met). To bind yeast-initiating Met-tRNA(i) (Met) to ribosomes, initiation factors present in a ribosomal wash fraction from yeast are needed.

Binding Sites↗
PubMed1971

Pantetheine-linked peptide intermediates in gramicidin S and tyrocidine biosynthesis.

To study the function of pantetheine in gramicidin S and tyrocidine biosynthesis, pepsin digests of the polymerizing enzymes, of which only the heavy ones contain pantetheine, were analyzed. The digests of gramicidin S enzymes charged with either [(14)C]proline or with D-phenylalanyl-[(14)C]proline, were analyzed by thin-layer chromatography; only the dipeptide showed a derivative associated with pantetheine. Similar results were obtained from the heavy tyrocidine enzyme charged with either [(14)C]asparagine alone or with the pentapeptide D-Phe-Pro-Phe-D-Phe-[(14)C]Asn. Several radioactive products appeared on the thin-layer chromatograms of both these digests; association with pantetheine was found only in the case of the pentapeptide. Exposure of the chromatogram from the pentapeptide-labeled digest to performic acid and development in a second direction separated the peptide from pantetheine, indicating that a nascent peptide was originally linked to the cofactor by a thioester bond. The connection of pantetheine only with peptide residues appears to confirm its role in transpeptidation during peptide chain growth.

Asparagine↗