Mutations in genes cpxA and cpxB of Escherichia coli K-12 cause a defect in acetohydroxyacid synthase I function in vivo.
AUTOR(ES)
Sutton, A
RESUMO
Mutations in Escherichia coli genes cpxA and cpxB together cause a temperature-sensitive defect in isoleucine and valine syntheses that is related specifically to acetohydroxyacid synthase I. This enzyme catalyzes the first pair of homologous reactions required for the synthesis of these two amino acids. At both permissive and nonpermissive temperatures, mutant cells containing ilvB (the structural gene for acetohydroxyacid synthase I) cloned in a derivative of plasmid pBR322 synthesized comparable amounts of ilvB mRNA and contained several times the enzyme activity normally required to sustain exponential growth, yet these cells remained temperature sensitive for growth in the absence of isoleucine and valine. These observations suggest that the primary effect of the cpx mutations is to block enzyme function in vivo. The enzyme was unstable in mutant cells at growth temperatures above 37 degrees C, but this instability appeared to be a secondary effect on the cpx mutations.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=220350Documentos Relacionados
- Mutations in genes cpxA and cpxB of Escherichia coli K-12 cause a defect in isoleucine and valine syntheses.
- Synthesis of outer membrane proteins in cpxA cpxB mutants of Escherichia coli K-12.
- Mutations in genes cpxA and cpxB alter the protein composition of Escherichia coli inner and outer membranes.
- Genetic analysis of Escherichia coli K-12 chromosomal mutants defective in expression of F-plasmid functions: identification of genes cpxA and cpxB.
- The ilvB locus of Escherichia coli K-12 is an operon encoding both subunits of acetohydroxyacid synthase I.