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H G Wittmann

Publications and source records attributed to H G Wittmann.

At least 55 records · Page 3Linked to original sources
PubMed1980

Structure and evolution of ribosomes.

Ribosomes are multicomponent particles on which biosynthesis of proteins occurs in all organisms. The best-known ribosome, namely that of E. coli, consists of three RNA's and 53 different proteins. All proteins have been isolated and characterized by chemical, physical, and immunological methods. the primary sequences of 49 E. coli ribosomal proteins have so far been determined. Studies of the shape, as well as of the secondary and tertiary structure, of the proteins are in progress. Various techniques, 3.g., immune electron microscopy and cross-linking of neighboring components in situ, give information about the architecture of the ribosomal particle. The first technique resulted in illustrative and detailed knowledge now only on the shape of the ribosomal subunits but also about the location of many proteins on the surface of the particles. The analysis of cross-links between ribosomal proteins and/or RNA's has in several cases been pursued to the level of elucidating which amino acids and/or nucleotides are cross-linked together in situ. Reconstitution of a fully active E. coli 50S ribosomal subunit from its isolated RNA and protein components can be accomplished by means of a two-step incubation procedure. From the analysis of the intermediates occurring during the reconstitution process it has been concluded that the in vitro reconstitution process resembles that in vivo assembly of 50S subunits in many respects. E. coli mutants with alterations in almost all ribosomal proteins have been isolated. Their biochemical and genetic analyses are very useful tools for obtaining information about the structure, function, and biosynthesis of ribosomes, as well as about the location of the genes for these proteins on the chromosome. From comparative electrophoretic, immunological, protein-chemical, and reconstitution studies on ribosomes from various species it has become clear that their is little homology between ribosomal proteins from prokaryotes and those from eukaryotes. This finding is surprising since there is no essential difference in the way in which pro-and eukaryotic ribosomes function in protein biosynthesis.

Amino Acid Sequence↗
PubMed1980

Ribosomal function and its inhibition by antibiotics in prokaryotes.

Most of the known antibiotics act at the level of protein biosynthesis probably due to the extraordinary complexity of the translation machinery which can be interfered with at many points. At first a survey is given of our present knowledge covering the structure and function of the prokaryotic ribosome. The most important antibiotics acting at the translational level are integrated into this network of data. The binding sites and the inhibition mechanisms of the drugs, together with the ribosomal components altered in resistant mutants are described. Finally, the points of interference with the translational machinery are indicated in an extended scheme of ribosomal functions.

Anti-Bacterial Agents↗
PubMed1978

Ribosome structure.

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Amino Acid Sequence↗
PubMed1977

Improved electrophoretic and immunochemical techniques for the identification and characterization of mutant proteins, applied to ribosomal protein S8 in Escherichia coli mutants.

The ribosomal proteins of 11 mutants which are sensitive to starvation at elevated temperature and of 36 transductants derived from them were studied with several electrophoretic, immunochemical and proteinchemical methods. The following results were obtained: (1) Ribosomal protein S8 is altered in three of these mutants. (2) The amino acid exchange in proteins S8 of mutant N4128 is Glu leads to Lys in position 59 of the protein chain. (3) Temperature sensitivity and inability to recover from starvation at elevated temperatures are caused by the same mutational event which is, however, unrelated to the alteration in protein S8. Several electrophoretic and immunological procedures were applied during the characterization of these mutants. A modified immunoelectrophoresis on cellulose acetate gels was developed, and proved to be the most applicable procedure for the detection of mutationally altered ribosomal proteins. This procedure may gain general importance for detecting mutational alterations in other proteins.

Amino Acid Sequence↗
PubMed1977

Cold-sensitive growth of a mutant of Escherichia coli with an altered ribosomal protein S8: analysis of revertants.

26 cold-resistant revertants of a cold-sensitive Escherichia coli mutant with an altered ribosomal protein S8 were analyzed for their ribosomal protein pattern by two-dimensional polyacrylamide gel electrophoresis. It was found that 16 of them had acquired the apparent wild-type form of protein S8, one exhibits a more strongly altered SC than the original mutant and two revertants regained the wildtype form of S8 and, in addition, possess alterations in protein L30. The ribosomes of the residual revertants showed no detectable difference from those of the parental S8 mutant. The mutation leading to the more strongly altered S8 was genetically not separable from the primary S8 mutation; this indicates that both mutations are very close to each other or at the same site. The structural gene for ribosomal protein L30 was mapped relative to two other ribosomal protein genes (for proteins S5 and S8) by the aid of one of the L30 mutants: The relative order obtained is: aroE....rpmD(L30)....rpsE(S5)....rpsH(S8)....rpsL(S12). The L30 mutation impairs growth and ribosomal assembly at 20 degrees C and is therefore the first example of a mutant with defined 50S alteration that has (partial) cold-sensitive ribosome assembly. A double mutant was constructed which possesses both the S8 and the L30 mutations. It was found that the L30 mutation had a slight antagonistic effect on the growth inhibition caused by the S8 mutation. Thus the L30 mutants might have possibly arisen from the original S8 mutant first as S8/L30 double mutants which was followed by the loss of the original S8 lesion.

Cold Temperature↗
PubMed1977

Erythromycin resistant mutations in Bacillus subtilis cause temperature sensitive sporulation.

All of several hundred erythromycin resistant single site mutants of Bacillus subtilis W168 are temperature senstive for sporulation. The mutants and wild type cells grow vegetatively at essentially the same rates at both permissive (30 degrees C) and nonpermissive (47 degrees C) temperatures. In addition cellular protein synthesis, cell mass increases and cell viabilities are similar in mutant and wild type strains for several hours after the end of vegetative growth (47 degrees C). in the mutants examined, the temperature sensitive periods begin when the sporulation process is approximately 40% completed, and end when the process is 90% completed. At nonpermissive temperatures, the mutants produce serine and metal proteases at 50% of the wild type rate, accumulate serine esterase at 16% of the wild type rate, and do not demonstrate a sporulation related increase in alkaline phosphatase activity. The eryR and spots phenotypes cotransform 100%, and cotransduce 100% using phage PBS1. Revertants selected for ability to sporulate normally at 47 degrees C (spot), simultaneously regain parental sensitivity to erthromycin. No second site revertants are found. Ribosomes from eryR spots strains bind erythromycin at less than 1% of the wild type rate. A single 50S protein (L17) from mutant ribosomes shows an altered electrophoretic mobility. Ribosomes from spo+ revertants bind erythromycin like parental ribosomes and their proteins are electrophoretically identical to wild type. These data indicate that the L17 protein of the 50S ribosomal subunit from Bacillus subtilis may participate specifically in the sporulation process.

Bacillus subtilis↗