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Biomedical subjects

D W Schultz

Publications and source records attributed to D W Schultz.

30 records · Page 2Linked to original sources
PubMed1983

Nucleotide sequence of the lysozyme gene of bacteriophage T4. Analysis of mutations involving repeated sequences.

The nucleotide sequence of the lysozyme (e) gene of bacteriophage T4 and approximately 130 additional nucleotides on each side has been determined. The 5'-end of the gene for internal protein III appears to be located about 70 base-pairs from the 3'-end of the lysozyme gene. Nucleotide sequence analysis of mutant e genes confirmed that three identified hotspots of frameshift mutations are runs of five A nucleotides in the wild-type gene. The endpoints of two deletions are direct repeats of eight base-pairs in the wild-type gene. Two frameshift mutations with high reversion frequencies are duplications of five or seven base-pairs. The cloning and nucleotide sequence determination of the lysozyme gene will facilitate further study of the molecular biology of T4 lysozyme.

Base Sequence↗
PubMed1983

Escherichia coli RecBC pseudorevertants lacking chi recombinational hotspot activity.

Pseudorevertants of an Escherichia coli exonuclease V (RecBC enzyme)-negative mutant have been isolated after ethyl methane sulfonate mutagenesis of a recC73 (presumed missense) mutant. The remedial mutations in each of the four pseudorevertants studied in detail map and complement as recC mutations. By several criteria, such as recombination proficiency, support of phage growth, RecBC nuclease activity, and cell viability, the pseudorevertants appear to have regained partially or completely various aspects of RecBC activity. However, chi recombinational hotspots, which stimulate exclusively the RecBC pathway of recombination, have no detectable activity in lambda vegetative crosses in the pseudorevertants. The properties of these mutants, in which the RecBC pathway of recombination is active yet in which chi is not active, are consistent with the hypothesis that wild-type RecBC enzyme directly interacts with chi sites; alternatively, the mutants may block or bypass the productive interaction of another recombinational enzyme with chi.

Coliphages↗
PubMed1981

Structure of chi hotspots of generalized recombination.

Chi recombinational hotspots are sites around which the rate of Rec-promoted recombination in bacteriophage lambda is elevated. Examination of a derivative of lambda into which the plasmid pBR322 was inserted reveals that pBR322 lacks Chi sites. Using this lambda-pBR322 hybrid, we obtained mutations creating Chi sites at three widely separated loci within pBR322. Nucleotide sequence analysis reveals that the mutations are single base-pair changes creating the octamer 5' GCTGGTGG 3'. This sequence is present at three previously analyzed Chi sites in lambda, and all analyzed mutations creating or inactivating these Chi sites occur within this octamer. We conclude that Chi is 5' GCTGGTGG 3', or its complement, or both.

Bacteriophage lambda↗
PubMed1981

Nucleotide sequence of the chi recombinational hot spot chi +D in bacteriophage lambda.

Chi sites in bacteriophage lambda stimulate recombination promoted by the RecBC pathway of Escherichia coli. Mutations which create these sites occur at four widely separated loci in lambda. We report here the nucleotide sequence surrounding the site of one of these loci, chi D, located near the S gene. The mutations creating the active Chi site, designated chi +D, are transversions from CG to AT. This mutation, like the chi +B and chi +C mutations previously analyzed, leads to a nucleotide sequence common to all three active chi sites.

Bacteriophage lambda↗
PubMed1980

Generalized recombination: nucleotide sequence homology between Chi recombinational hotspots.

Chi sites stimulate generalized recombination catalyzed by the RecA-RecBC-dependent system of E. coli. This stimulation occurs over a region of several thousand base pairs surrounding the Chi site. These sites arise by mutation at four distinct loci in bacteriophage lambda. We report here the nucleotide sequence surrounding one of these loci, chi B, located between the xis and reda genes. Alteration of a single GC base pair, by deletion or by transversion to a CG base pair, creates the Chi recombinational hotspot chi + B. In a section of 30 bp, the chi + B sequence has 23 bp in common with the chi + C sequence determined previously. We presume that some part of this common sequence is the recognition sequence for a protein which acts at a rate-limiting step of generalized recombination.

Bacteriophage lambda↗