Selective acylation of plasma membrane proteins of Mycoplasma agalactiae: The causal agent of agalactia

Revealed by in vivo labeling with C-14-palmitic acid, about 15 acylated pro teins were identified in the plasma membrane of Mycoplasma agalactiae (type strain PG2), including the major component p40. Triton X-114 phase partiti oning and Western blotting demonstrated the amphiphilic properties of the a cyl proteins and showed that they were also antigenic components. Chemical analyses of fatty acids bound to proteins revealed the following selectivit y order within acylation: stearic acid (18:0) > Linoleic acid (18:2c) appro ximate to palmitic acid (16:0) > oleic acid (18:1c) > myristic acid (14:0), with 16:0 and 18:le preferred for the O-acylation and 18:0 for the N-acyla tion. The ratio [O-ester- + amide-bound acyl chains]/O-ester-linked chains being close to 1.4 as well as the presence of S-glycerylcysteine suggest th at acyl proteins in M. agalactiae are true lipoproteins containing N-acyl d iacyl glycerylcysteine, probably processed by a mechanism analogous to that described for Gram-negative eubacteria.