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Biomedical subjects

H Weissbach

Publications and source records attributed to H Weissbach.

At least 163 records · Page 9Linked to original sources
PubMed1975

Guanylate cyclase in Escherichia coli. Purification and properties.

Guanylate cyclase has been purified from extracts of Escherichia coli. After a 1000-fold purification, the enzyme contains only minor contaminants as judged by disc gel electrophoresis. The Km for GTP is approximately 7 times 10(-5) M and the optimal pH is 8.0. More activity is observed with Mn2+ than with Mg2+, and maximal activity is observed at 0.14 mM Mn2+ and 1.4 mM Mg2+. Based on its behavior on Sephadex G-100, the molecular weight of E. coli guanylate cyclase is about 30,000. Disc gel electrophoretic analysis indicates that the enzyme consists of a single polypeptide chain. Guanylate cyclase does not form 3':5'-AMP from ATP, and therefore, is distinct from adenylate cyclase.

Enzyme Activation↗
PubMed1975

Transport in an Escherichia coli fatty acid auxotroph. A novel case of catabolite repression.

The transport of alpha-methylglucoside and a variety of amino acids including histidine, leucine, lysine, proline, and threonine are reduced 5- to 50-fold in Escherichia coli K1061, an unsaturated fatty acid auxotroph, when cells are grown in medium containing glucose as a carbon source and supplemented with either cis-vaccenic acid or cis-9, 10-methylenehexadecanoic acid. Cells grown in glucose medium containing oleate, palmitoleate, or cis-7-hexadecenoate do not exhibit this effect and transport alpha-methylglucoside and amino acids at rates comparable to those of a wild type strain. For cis-vaccenate- and cis-9, 10-methylenehexadecanoate-grown cells the capacity to transport amino acids and alpha-methylglucoside is normal when glycerol or succinate is the energy supply or when cyclic adenosine 3':5'-monophosphate is added to cultures growing on glucose. These results suggest that in this strain several transport systems are affected by catabolite repression, but the phenomenon is unique since repression requires not only glucose but specific unsaturated fatty acids, cis-vaccenic acid, or cis-9, 20-methylenehexadecanoic acid.

Biological Transport, Active↗
PubMed1975

Purification and properties of a soluble factor required for the deoxyribonucleic acid-directed in vitro synthesis of beta-galactosidase.

The DNA-directed in vitro synthesis of beta-galactosidase has been investigated in a system dependent on Escherichia coli ribosomes, a salt wash of the ribosomes, and a supernatant fraction. Fractionation of the supernatant has made it possible to obtain dependencies on RNA polymerase and another protein factor for beta-galactosidase synthesis. The other factor (called L factor) cannot be replaced by a variety of proteins known to be required for transcription and translation. It has been purified to homogeneity and has a molecular weight of approximately 65,000. Although it is required for the in vitro synthesis of beta-galactosidase, it has no effect on total DNA-dependent amino acid incorporation under the conditions of the incubation. However, total RNA synthesis is depressed by the addition of L factor in a manner similar to what is observed with rho factor could not replace L factor in beta-galactosidase synthesis.

Amino Acyl-tRNA Synthetases↗
PubMed1975

Stimulation of the uptake of soluble proteins into isolated HeLa nuclei by pancreatic deoxyribonuclease.

The uptake into isolated HeLa nuclei of radioactive cytosol proteins and purified Escherichia coli ribosomal protein L7 is stimulated up to 4-fold by pancreatic deoxyribonuclease (DNase I). Similar effects are not observed with pancreatic ribonuclease A or phospholipase C. The results reported suggest that there is a general stimulatory effect of DNase on protein uptake by nuclei.

Bacterial Proteins↗
PubMed1974

The requirement for ribosomal proteins L7 and L12 in peptide-chain termination.

Proteins L7 and L12 from 50S ribosomal subunits of Escherichia coli are required for peptidechain termination. This termination process is inhibited by thiostrepton. Since both thiostrepton-treated ribosomes and those depleted of L7 and L12 have a markedly reduced ability to form release factor.UA[(3)H]A.ribosome complexes, the binding of release factors to the ribosome appears to be the primary site of inhibition.

Anti-Bacterial Agents↗
PubMed1974

Role of phospholipids in the multiple forms of mammalian elongation factor 1.

Evidence is presented that high-molecular-weight aggregates of elongation factor 1 from calf brain and liver contain phospholipids. Sucrose gradient analysis has shown that these high-molecular-weight species can be converted to a low-molecular-weight form after incubation with different phospholipase preparations. In addition, a partially purified elongation factor 1 from rabbit reticulocytes is also converted to a low-molecular-weight species by phospholipase treatment. These data indicate that phospholipids are involved in maintaining the integrity of the high-molecular-weight species and support the view that this species is an aggregate of the low-molecular-weight elongation factor 1.

Animals↗