FIG. 2.

Enzymatic activity of TarI-His (Spr1149-His). (A) Analysis of TarI-His by SDS-gel electrophoresis. The protein was separated by SDS-12% PAGE, followed by staining with Coomassie blue. Lane 1, TarI-His; M, molecular size marker. The molecular masses of the marker proteins are indicated on the left side. (B) Assay to detect the release of pyrophosphate by TarI-His. The complete sample (left side) contained Spr1149-His, ribitol 5-phosphate (ribitol-5P), CTP, and pyrophosphatase (PPase), the latter converting pyrophosphate to phosphate, which was detected in the malachite green assay. Either control samples lacked one of the assay components, or the components were tested alone for the presence of phosphate. Other possible substrates (2-l-methyl-d-erythritol [MEP], glycerol 1-phosphate [G3P], and phosphorylcholine [Cho-P]) were also tested with TarI or in the absence of enzyme (controls). TarI-His released pyrophosphate from CTP in the presence of ribitol 5-phosphate and MEP but not glycerol 1-phosphate and phosphorylcholine.