Procedure for purification of Escherichia coli ribonucleic acid synthesis termination protein .rho

An improved purification procedure is described for the rho transcription termination factor of Escherichia coli. The method involves lysozyme--sodium deoxycholate lysis, Polymin P fractionation, and chromatography on phosphocellulose, poly(uridylic acid)--Sepharose, and AMP--agarose. The method yields up to 9 mg of electrophoretically pure protein from 200 200 g of E. coli MRE 600. From quantitative amino acid analysis rho is calculated to have an E280nm (1%) of 3.7 +/- 0.3. The purified rho has an ATPase specific activity of 32 nmol of Pi released min-1 microgram-1 when poly(cytidylic acid) is used as a cofactor, and it functions effectively in termination of T7 DNA transcription. A subunit molecular weight of 48 000 for rho was determined by phosphate-buffered sodium dodecyl sulfate--polyacrylamide gel electrophoresis. The amino acid composition and circular dichroism spectrum in the far-ultraviolet for rho are presented.