Showing papers on "hisB published in 1973"
TL;DR: HisB mutants of Salmonella typhimurium have been screened to determine the molecular size of the resulting histidinol phosphate phosphatase activity, one of the activities of a bifunctional enzyme produced by this gene which also controls imidazole glycerol phosphate dehydrase activity.
Abstract: Forty-three hisB mutants of Salmonella typhimurium have been screened to determine the molecular size of the resulting histidinol phosphate phosphatase activity, one of the activities of a bifunctional enzyme produced by this gene which also controls imidazole glycerol phosphate dehydrase activity. Mutation in hisB can lead to the loss of both phosphatase and dehydrase activities, or only of dehydrase activity. Through the use of nonsense mutants lacking dehydrase activity, a distinct point of transition was detected near the middle of hisB at which a dramatic change occurs in the size of the phosphatase enzyme that is synthesized. A missense mutant with a lesion in this region has a high-molecular-weight enzyme which is eluted in the void volume of a Sephadex G-200 column. The enzyme from nonsense mutants near the transition point have molecular weights near 40,000. Even though the buffer conditions are designed to favor the stabilization of the high-molecular-weight form, some mutants have both high- and low-molecular-weight forms. The polypeptide chain specified by the operator proximal part of hisB is sufficient to allow the expression of phosphatase activity. The synthesis of substantially less than the complete product of hisB resulted in association into a form similar to the native enzyme which was found in the void volume of a Sephadex G-200 column.
15 citations
TL;DR: A distinct change occurs in the molecular size of the enzyme, histidinol phosphate phosphatase, specified by nonsense mutants with lesions near the middle of hisB, which is likely to be produced by limited proteolysis of the 47,000 molecular weight form.
11 citations
TL;DR: Three electrophoretically separable forms of the phosphatase enzyme from Salmonella typhimurium were demonstrated, and all were shown to have a mol wt of approximately 38,000 and to consist of a single polypeptide chain.
Abstract: The gene products from hisB nonsense mutants having histidinol phosphate phosphatase activity were isolated from Salmonella typhimurium. The enzyme from strain TR691 (hisB278 hisT1529 aroD5) was isolated in the presence of diisopropylfluorophosphate. Three electrophoretically separable forms were demonstrated, and all were shown to have a mol wt of approximately 38,000 and to consist of a single polypeptide chain. Previously, two forms of the phosphatase enzyme from this strain were isolated without diisopropylfluorophosphate and shown to have a different subunit composition. Strain TA387 (hisB2133 his 01242) was shown to have two electrophoretically separable phosphatases with a mol wt of about 52,000 and consisted of 17,000- to 19,000-mol wt polypeptide chains as evidenced by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The results could be explained by proteolytic cleavage of the primary gene product which can partially be prevented by the protease inhibitor. Strain TA387 phosphatase lost all activity in 8 M urea but could be renatured by dialysis. Gel filtration showed that it also regained its original molecular weight. The values of Km of histidinol phosphate and the competition inhibition constant for histidinol were determined. The addition of MnCl2 to the assay was shown to shift the optimal pH value to a lower pH value.
8 citations