Defective replication activity of a dominant-lethal dnaB gene product from Escherichia coli.
dnaB protein of Escherichia coli is an essential replication protein. A missense mutant has been obtained which results in replacement of an arginine residue with cysteine at position 231 of the protein (P. Shrimankar, L. Shortle, and R. Maurer, unpublished data). This mutant displays a dominant-lethal phenotype in strains that are heterodiploid for dnaB. Biochemical analysis of the altered form of dnaB protein revealed that it was inactive in replication in several purified enzyme systems which involve specific and nonspecific primer formation on single-stranded DNAs, and in replication of plasmids containing the E. coli chromosomal origin. Inactivity in replication appeared to be due to its inability to bind to single-stranded DNA. The altered dnaB protein was inhibitory to the activity of wild type dnaB protein in replication by sequestering dnaC protein which is also required for replication. By contrast, it was not inhibitory to dnaB protein in priming of single-stranded DNA by primase in the absence of single-stranded DNA binding protein. Sequestering of dnaC protein into inactive complexes may relate to the dominant-lethal phenotype of this dnaB mutant.
Marszalek
J
J
Department of Biochemistry, Michigan State University, East Lansing 48824-1319.
Kaguni
J M
JM
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001667:Binding, Competitive; D004265:DNA Helicases; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D053488:DnaB Helicases; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005799:Genes, Dominant; D005804:Genes, Lethal; D046911:Macromolecular Substances; D013329:Structure-Activity Relationship
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; C071702:DnaC protein, E coli; D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D004265:DNA Helicases; D053488:DnaB Helicases