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Biomedical subjects

J Beckwith

Publications and source records attributed to J Beckwith.

At least 181 records · Page 10Linked to original sources
PubMed1978

Mutant RNA polymerase of Escherichia coli terminates transcription in strains making defective rho factor.

We have isolated a rifampicin-resistant mutant of Escherichia coli RNA polymerase that restores transcription termination in strains with a defective rho protein. In such strains, the mutant RNA polymerase terminates transcription at normally rho-dependent sites at the end of the trp operon, in bacteriophage lambda, and within the lac operon. In addition, a strain with this mutant RNA polymerase remains viable with an amber mutation in rho, whereas a strain with wild-type RNA polymerase does not. These results suggest that the mutant RNA polymerase can terminate transcription at normally rho-dependent sites in the absence of rho.

DNA-Directed RNA Polymerases↗
PubMed1977

Use of gene fusions to study outer membrane protein localization in Escherichia coli.

Escherichia coli strains have been isolated that produce hybrid proteins comprised of an NH2-terminal sequence from the lamB gene product (an outer membrane protein) and a major portion of the COOH-terminal sequence of beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23; a cytoplasmic protein). These proteins exhibit beta-galactosidase activity. One such strain, pop 3105, produces a hybrid protein containing very little of the lamB gene protein; the protein is found in the cytoplasm. The protein found in a second strain, pop 3186, contains much more of the lamB gene protein; a substantial fraction of the beta-galactosidase activity is found in the outer membrane, probably facing outward. These results indicate that information necessary to direct the lamB gene product to its outer membrane location is located within the lamB gene itself. The properties of such fusion strains open up the prospect of a precise genetic analysis of the genetic components involved in protein transport.

Bacterial Proteins↗
PubMed1977

Synthesis and processing of an Escherichia coli alkaline phosphatase precursor in vitro.

Alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] of E. coli was synthesized in a cell-free system, and the size of the direct translation product was analyzed. The product has a higher molecular weight than the mature alkaline phosphatase found in the periplasm. The direct translation product can be processed to the mature size by an E. coli membrane fraction; the processing activity copurifies with the outer-membrane fraction. The presumed precursor can dimerize to form active enzyme without being processed, and the resultant enzyme appears to be more hydrophobic than the mature enzyme. These findings are discussed in connection with the "signal hypothesis" proposed for the excretion of proteins across membranes.

Alkaline Phosphatase↗
PubMed1975

Deletion of the Escherichia coli crp gene.

Spontaneous crp mutants Escherichia coli were selected from a strain that does not require 3',5'-cyclic adenosine monophosphate for CAP activity. Several deletions of the crp gene were characterized. The crp gene was not essential for growth of E. coli. crp mutations reduced the donor ability of Hfr strains.

Adenylyl Cyclases↗
PubMed1973

Cyclic adenosine monophosphate-independent mutants of the lactose operon of Escherichia coli.

In Escherichia coli the transcription of the lactose operon, like other catabolite-sensitive operons, requires catabolite gene activator protein and 3',5'-cyclic adenosine monophosphate in addition to ribonucleic acid polymerase. We isolated and analyzed lac(+) revertants from a crp(-) strain of E. coli. We found that revertants with a higher level of expression only for the lac operon lie in the lac promoter region. These promoter mutations have no effect on operator or repressor function. Two of the revertants in which the lesions have been more precisely mapped carry mutations in the operator proximal segment of the promoter.

Bacterial Proteins↗
PubMed1973

Genetic characterization of mutations which affect catabolite-sensitive operons in Escherichia coli, including deletions of the gene for adenyl cyclase.

Sixty-two spontaneous mutations have been characterized which reduce the level of expression of catabolite-sensitive operons. These mutations appear to affect either the crp (catabolite gene activator protein) or cya (adenyl cyclase) loci. No new loci have been discovered. Deletions of the cya gene do not remove an essential function. phi80 transducing phage for the cya gene have been used to do recombination and complementation studies on cya mutants.

Adenylyl Cyclases↗
PubMed1970

Mechanism of activation of catabolite-sensitive genes: a positive control system.

Catabolite repression is defined as the inhibition of enzyme induction by glucose or related substances. In the bacterium E. coli, the effect of glucose appears to be due to a lowering of the cyclic AMP level. A DNA-directed cell-free system for beta-galactosidase synthesis has served as a model system for studying the mechanism of action of cyclic AMP. Previously, it was reported that in this system cyclic AMP is required for normal initiation of mRNA synthesis. A protein factor which acts in conjunction with the cyclic AMP has been partially purified. This protein factor has a high affinity for cyclic AMP. These and other results presented herein lead us to the conclusion that cyclic AMP and a protein factor called the catabolite gene activator protein are part of a positive control system for activating catabolite-sensitive genes.

Adenine Nucleotides↗