SELECTIVE ACYLATION OF PLASMA-MEMBRANE PROTEINS OF MYCOPLASMA-MYCOIDES SUBSP MYCOIDES SC, THE CONTAGIOUS BOVINE PLEUROPNEUMONIA AGENT

The plasma membrane of Mycoplasma mycoides subsp. mycoides SC (strain KH(3)J) contains over 160 polypeptides with apparent molecular masses ranging from 14 to 125 kDa and isoelectric point values (pIs) from 5 t o 9. In vivo labeling with [C-14]-fatty acids revealed about 35 acylat ed polypeptides including the two major components p42 and p65 and dis playing pls between 5.5 and 9.0, with a majority between 6.5 and 8. Th e amphiphilic nature of most of these acyl proteins was confirmed by T riton X-114 phase partitioning. Gas-liquid chromatography analyses sho wed that the order of preference for protein acylation was 16:0 > 18:2 c > 18:1c > 18:0 > 14:0, with 16:0 being the major O-ester-bound fatty acyl chain and 18:2c the major N-linked chain. The presence of S-glyc erylcysteine and a ratio of [O-ester-bound acyl chains + N-linked chai ns]/O-ester bound chains of approximate to 1.2 in M. mycoides subsp. m ycoides SC membrane proteins are consistent with a lipid modification similar to that occurring in lipoproteins of Gram-negative eubacteria that contain an N-terminal acyl S-glycerylcysteine.