INTERACTION OF AVIDIN WITH SPIN-LABELED N-BIOTINYL PHOSPHATIDYLETHANOLAMINE IN A LIPID-MEMBRANE

N-Biotinyl phosphatidylethanolamine spin labelled at the C-14 position of the sn-2 chain has been incorporated at a level of 1 mol% in bilayers of dimyristoyl phosphatidylcholine, and the effects on the chain mobility of binding avidin to the biotin lipid headgroup have been studied by electron spin resonance spectroscopy. In the fluid phase, avidin causes a large and selective restriction in the chain motion of the biotin lipids to which it is attached, without perturbing appreciably the mobility of the bulk lipid chains. This specific type of lipid-protein interaction is different in kind from that observed both with integral and peripheral membrane proteins and may be involved in transmembrane communication on ligand binding to lipid headgroups, as well as lateral communication (at high packing densities) between proteins with covalent lipid anchors.