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C Georgopoulos

Publications and source records attributed to C Georgopoulos.

137 records · Page 8Linked to original sources
PubMed1982

Evidence that the two Escherichia coli groE morphogenetic gene products interact in vivo.

The Escherichia coli groEL and groES gene products are essential for both phage morphogenesis and bacterial growth. Although the gene products have been identified, their exact roles in these processes are not known. We have isolated mutations in the groEL gene that suppress defects in the groES gene. These intergenic suppressors were shown to map in the groEL gene by a variety of genetic and biochemical analyses. These results suggest that the two morphogenetic gene products interact in vivo and help to explain why mutations in either gene exhibit the same phenotype with respect to lambda head assembly and bacterial growth.

Bacterial Proteins↗
PubMed1982

The B66.0 protein of Escherichia coli is the product of the dnaK+ gene.

B66.0 is one of the most abundant proteins of Escherichia coli. Its relative rate of synthesis is highly regulated depending on temperature and the growth rate of the culture. We identified the B66.0 protein to be the dnaK+ structural gene product since dnaK756 mutant bacteria synthesized a B66.0 protein with a more acidic isoelectric point.

Bacterial Proteins↗
PubMed1981

Identification of the E. coli groNB(nusB) gene product.

The E. coli groNB(nusB) gene product has been previously shown to be necessary for bacteriophage lambda N protein function. The product of the groNB gene has been identified on SDS polyacrylamide gels after infection of UV-irradiated E. coli cells with various lambda groNB+ transducing phage derivatives. It is a polypeptide with an apparent molecular weight of 14,000 daltons. Transducing phage carrying either a deletion or an amber mutation in the groNB gene fail to synthesize the 14,000-Mr polypeptide chain upon infection of a sup+ host. However, am+ revertants of the lambda groNBam phage do induce the synthesis of the polypeptide.

Bacterial Proteins↗
PubMed1981

Identification of a second Escherichia coli groE gene whose product is necessary for bacteriophage morphogenesis.

Previous work has uncovered the existence of an Escherichia coli locus, groE, that is essential for bacterial growth, lambda phage and T4 phage head morphogenesis, and T5 phage tail assembly. Our genetic and biochemical analyses of lambda groE+ transducing phages and their deletion and point mutant derivatives show that the groE locus consists of two closely linked genes. One groE gene, groEL, has been shown to encode the synthesis of a 65,000 Mr polypeptide, whereas the second, groES, codes for the synthesis of a 15,000 Mr polypeptide. About half of the groE- bacterial isolates fall into the groES complementation group. GroE mutations in either gene cause similar phenotypes, with respect to lambda phage head morphogenesis and bacterial growth at nonpermissive temperatures.

Coliphages↗
PubMed1981

Studies on Escherichia coli mutants which block bacteriophage morphogenesis.

We have previously reported the isolation of E. coli groE mutants, which block lambda head morphogenesis. Further analysis of these mutants showed that many are temperature-sensitive for bacterial growth or block the growth of the unrelated phages T4 and T5. We have established the existence of a second groE gene, which we call groES, that is different from the previously described groE gene encoding a 65,000-Mr polypeptide (Georgopoulos and Hohn, 1978; Hendrix and Tsui, 1978) and which is renamed groEL. Genetic and biochemical studies of lambda groE+ transducing phages and their mutant derivatives show that these two genes are closely linked and that the groES gene codes for a polypeptide of 15,000-Mr. Bacterial groEL- or groES- mutants exhibit the same growth kinetics and phenotype at high temperature and lambda proheads have the same protein composition in both classes of mutants.

Bacterial Proteins↗
PubMed1981

Bacteriophage-host interactions in assembly.

Because of their small genome size and their parasitic way of life, bacteriophages have obligatorily evolved in such a way as to efficiently utilize many of the bacterial functions necessary for DNA replication, transcription, translation, and morphogenesis. In many instances the phage and host functions act in parallel in these processes, e.g. T4 and host DNA ligase. The specific nature of the host's contribution to phage morphogenesis is being pursued by the studies summarized here. The isolation and characterization of bacterial mutants which block phage morphogenesis, albeit at a preliminary stage, has already contributed considerable genetic information about the host's role. Future biochemical experiments, such as in vitro reconstitution, will help define the level of action of these bacterial gene products in the phage assembly process.

Bacterial Proteins↗
PubMed1980

Bacteriophage lambda cloning vehicles for studies of genetic recombination.

A pair of bacteriophage lambda cloning vehicles has been constructed for use in studies of genetic recombination. These phages, lambda rva and lambda rvb, have the following properties: (1) Each vector has a single HindIII site in the immunity region, at which segments of DNA can be inserted. (2) These HindIII sites are flanked by selectable markers with the following phenotypes: Spi+/- (Fec+/-) to the left, and imm lambda or imm434 to the right. (3) There is essentially no sequence homology between the two phages in this region, so recombination of the markers at reasonable frequency depends on the presence of homologous inserts at the HindIII sites. As a consequence, recovered recombinants must have resulted from a crossover event within the insert DNA. Restriction enzyme maps of the vectors have been determined. Variants of the original vectors have been isolated which permit separate examination of the viral (Red) and bacterial (Rec) generalized recombination mechanisms, and which provide a standard interval to which frequencies of recombination in cloned DNAs can be compared.

Bacteriophage lambda↗
PubMedDate not supplied

Biochemical properties of the Escherichia coli dnaK heat shock protein and its mutant derivatives.

The dnaK protein of Escherichia coli has been shown to possess both autophosphorylating and 5'-nucleotidase activities. The dnaK protein has been shown to bind avidly to ATP, but hydrolyzing it slowly. In vitro autophosphorylation occurs at a threonine residue when either ATP or GTP are used as phosphate donors. The extent of autophosphorylation is low; only a few percent of the molecules are phosphorylated. This activity is stimulated at least tenfold in the presence of Ca2+ ions with either ATP or GTP as the donor. The autophosphorylating activity of the mutant dnaK756 protein in the presence or absence of Ca2+ is reduced compared to that of the wild type.

Amino Acids↗
PubMedDate not supplied

Complex phenotypes of null mutations in the htr genes, whose products are essential for Escherichia coli growth at elevated temperatures.

Transposon insertion, followed by screening, has allowed the identification of a set of genes, called htr, whose products are required for Escherichia coli growth at elevated temperatures. The htrB gene has been shown to map at 23.5 min on the E. coli genetic map. It codes for a very basic, hydrophobic, 35,000-Mr polypeptide, possessing a putative membrane-spanning domain. At the non-permissive temperature, htrB mutant bacteria stop dividing, followed by the formation of bulges and eventual lysis. The htrC gene maps at 90 min, is under sigma 32 regulation and codes for a 21, 130-Mr polypeptide. At 43 degrees C, htrC mutant bacteria gradually lyse, whereas at intermediate temperatures they filament extensively. Finally, the htrM gene maps at 81 min, is under sigma 32 regulation and codes for a 35,000-Mr polypeptide. The HtrM null phenotype included inability to grow above 42 degrees C, extreme mucoidness and sensitivity to bile salts, even at the permissive temperatures. The htrM gene is identical to the rfaD gene, whose product is required for the biosynthesis of the lipopolysaccharide precursor ADP-L-glycero-D-mannoheptose (Pegues et al., J. Bact., 1990, 172, 4652-4660).

Bacterial Proteins↗