Characterization and composition of the purple and red membrane from Halobacterium cutirubrum;.

Abstract

The purple membrance (bacteriorhodopsin) isolated from cells of Halobacterium cutirubrum grown anaerobically in the light was shown to contain 77% protein and 20% lipils by weight. The protein component consisted of a single protein moeity, having a molecular weight of (19.6 plus or minus 0.8) times 10-3, complexed with retinal in mole ratio of 2:1, respectively. The protein moeity is not glycosylated but may be phosphorylated (ca. 2 mol of phosphate per mole of protein). The red membrance contains 56%protein and 38% lipids, including bacterioruberins. Several polypeptide components are present including some which may be glycosylated and/or phosphorylated. The lipids of both membranes contained phosphatidyl glycerophosphate (52%) and phosphatidyl glycerol (3-4%) but the sulfated lipid components, glycolipid sulfate and phosphatidyl glycerosulfate, were present exclusively in the purple membrane, the red membrane containing instead two unidentified glycolipids. Neutral lipids (squalenes, vitamin 75-8, etc.) were present in both membranes to the extent of 7-9%.