MEMBRANE-ASSOCIATED PHOSPHOLIPO-PROTEINS OF BACILLUS-LICHENIFORMIS 749

The membrane-bound penicillinase of B. licheniformis 749/C is a phospholipoprotein that differs from the hydrophilic exoenzyme in that its polypeptide chain carries an additional 25 residues (mostly hydrophilic) with phosphatidylserine as the NH2-terminus. To determine if other phospholipoproteins are present in the plasma membrane, the penicillinase-inducible strain 749 was grown without inducer in the presence of [2-3H] glycerol. Electrophoretic separation of the membrane proteins (after removel of free lipids) showed an association of 3H-activity with certain of the proteins which were not broken by lipid solvents and strongly denaturing conditions. Pronase digestion of the membrane proteins (after solvent extraction) released phosphatidylserine, indicating the covalent linkage of protein and phospholipid. Treatment of the isolated membranes with trypsin solubilized the protein portion of some of the phospholipoproteins (as with penicillinase), but not the 3H-labeled fragment. Penicillinase may be considered as the 1st observed example of a group of phosphatidylserine-containing proteins present in the plasma membrane of B. licheniformis 749 and 749/C.