| Abstrakt: |
The effect of altered lipid A synthesis on the synthesis of the OmpA protein was investigated in mutants of Salmonella typhimurium possessing a temperature-sensitive defect in 3-deoxy-D-manno-octulosonate (2-keto-3-deoxyoctonate) synthesis. The defect is due to a mutation in the structural gene for 3-deoxy-D-manno-octulosonate-8-phosphate synthetase (designated kdsA), and expression of this lesion results in the accumulation of an incomplete precursor of lipid A (Rick, P.D., and Osborn, M.J. (1977) J. Biol. Chem. 252, 4895-4903). Pulse labeling studies revealed a pronounced transient increase in the rate of OmpA synthesis following a shift of mutants to nonpermissive conditions. The rate of OmpA synthesis increased about 2.5-fold at 20-30 min following a shift to 42 degrees C and then decreased over the next 30-40 min. A similar but less pronounced increase in the apparent rate of synthesis of the 34-kilodalton porin protein was also observed. In contrast, the rates of synthesis of total cell envelope protein, as well as that of the 35 and 36-kilodalton porin proteins, were relatively unaffected. The effect of increased temperature on the rate of OmpA synthesis was specifically related to expression of the kdsA lesion; it was not found to be strain-specific or uniquely related to expression of a single kdsA mutant allele. |
