A mutant HemA protein with positive charge close to the N terminus is stabilized against heme-regulated proteolysis in Salmonella typhimurium.

ABSTRACT: The HemA enzyme (glutamyl-tRNA reductase) catalyzes the first committed step in heme biosynthesis in the enteric bacteria. HemA is mainly regulated by conditional protein stability; it is stable and, consequently, more abundant in heme-limited cells but unstable and less abundant in normally growing cells. Both the Lon and ClpAP energy-dependent proteases contribute to HemA turnover in vivo. Here we report that the addition of two positively charged lysine residues to the third and fourth positions at the HemA N terminus resulted in complete stabilization of the protein. By contrast, the addition of an N-terminal myc epitope tag did not affect turnover. This result confirms the importance of the N-terminal sequence for proteolysis of HemA. This region of the protein also contains a proline

SUBMITTER: Wang L 

PROVIDER: S-EPMC103631 | biostudies-literature | 1999 Oct

REPOSITORIES: biostudies-literature