IDENTIFICATION OF A COMPONENT SEPARATED ON MONO-Q PURIFICATION OF ESCHERICHIA-COLI RNA-POLYMERASE AS AN NTPASE

Standard preparations of Escherichia coli RNA polymerase (RNAP) contain NTPase activity. High-performance anion-exchange chromatography on Mono Q has recently been used by Hager et al. [1990, Biochemistry 29, 7890-7894] to fractionate RNAP into holoenzyme (alpha-2-beta-beta'-sigma) and core alpha-2-beta-beta') forms, plus other protein components. We found that one of these components, of protomer size slightly larger than the sigma-70 subunits, has NTPase activity; it is efficiently separated on Mono Q, leaving transcriptionally active holoenzyme and core apparently free of NTPase activity. Because of the similarity in size with sigma-70, the NTPase component may escape detection by routine gel electrophoresis.