Study of hydrophobic interactions between acylated proteins and phospholipid bilayers using BIACORE

Intracellular proteins of eukaryotic cells are frequently covalently modifi ed by the addition of long chain fatty acids. These modifications are thoug ht to allow otherwise soluble proteins to associate with membranes by lipid -lipid based hydrophobic interactions. The purpose of this work was to quan tify the effect of acyl chain length on hydrophobic interactions between ac ylated proteins and phospholipid monolayers. The binding of an artificially acylated model protein to electrically neutral phospholipids was studied b y surface plasmon resonance, using BIACORE, Kinetic rates for the binding o f bovine pancreatic ribonuclease A (RNase A), monoacylated on its N-termina l lysine with fatty acids of 10, 12, 14, 16 or 18 carbon atoms, to phosphol ipids on hydrophobic sensor chips, were measured. Unlike unmodified ribonuc lease, acylated RNase A bound to the phospholipids, and the association lev el increased with the acyl chain length to reach a maximum for C16, Reprodu cible kinetics were obtained which did not fit a 1:1 Langmuir model but rat her a two-step binding profile. Copyright (C) 2001 John Wiley & Sons, Ltd.