Effect of lipid acyl chain length on activity of sodium-dependent leucine transport system in Pseudomonas aeruginosa

The sodium-dependent leucine transport system of Pseudomonas aeruginosa was reconstituted into liposomes of binary lipid mixtures of dilauroylphosphatidylethanolamine (di(12:0)PE)/phosphatidylcholine (PC) with cis-monounsaturated fatty acid chains (di(n:1)PC) (n = 14-22) or dioleoylphosphatidylethanolamine (di(18:1)PE)/di(n:1)PC (n = 14-22). Leucine carrier proteins can be activated with phosphatidylethanolamine, whereas activation does not occur in PC-reconstituted vesicles (Uratani, Y., and Aiyama, A. (1986) J. Biol. Chem. 261, 5450-5454). Na+-dependent counterflow was measured at 30 degrees C as reconstituted transport activity. Proteoliposomes containing di(12:0)PE exhibited high counterflow activity at the PC acyl carbon number (n) of 18 and 20 but no or low activity at n = 14, 16, and 22. On the other hand, proteoliposomes containing di(18:1)PE exhibited higher transport activity than those vesicles with di(12:0)PE and corresponding di(n:1)PC. A lipid mixture of di(18:1)PE and di(16:1)PC supported maximal activity. These results show that the leucine transport system of P. aeruginosa is dependent on the lipid acyl chain length and suggest that there exists optimal bilayer thickness for maximal carrier activity.