Purification of the active mitochondrial phosphate carrier by affinity chromatography with an organomercurial agarose column

The general procedure for the isolation of the phosphate carrier from mitochondria involves solubilization with non-ionic detergents and chromatography on hydroxylapatite [l-3]. With high resolution SDS-gel electrophoresis this preparation can be separated into 4-5 protein bands [2]. Further purification, in particular removal of the ADP/ATP-carrier, was obtained by chromatography on Celite [2], on Mersalyl-Ultrogel [3,4] and by using Triton X-l 14 instead of Triton X-100 [5]. However, after all these procedures the purified phosphate carrier fraction still contained 4-5 protein bands in the &.-region of 30 000-35 000 [5]. Affi-Gel 501 (an organomercurial agarose gel), Dowex AG l-X8 and hydroxylapatite (Bio-Gel HTP) were obtained from Bio-Rad; [32P]phosphate (carrier free) from Amersham; [3H]NEM from New England Nuclear; acrylamide, N,N’methylenebisacrylamide, SDS, Triton X-100 and NEM from Serva; scintillation liquid (Maxifluor) from J. Baker; L-cY-phosphatidylcholine (from egg yolk, Type X-E) from Sigma and cardiolipin from Serdary.