Substrate-induced formation of a recognition structure in a four-polypeptide-lipid monolayer system

Abstract

Poly(γ-methyl L-glutamate)s with Ser, His, Asp, and Glu residues at the amino terminal as the serine protease catalytic site were prepared. The number-average degree of polymerization of the polypeptides was 51. A dipalmitoylphosphatidylcholine monolayer containing the polypeptides was formed at the air–water interface and was transferred onto gold-deposited glass plates. The binding of N-acetyltyrosine ethyl ester, a typical substrate of the serine protease, to the monolayer was characterized by surface plasmon resonance measurements. The four-polypeptide–lipid monolayer system conditioned on an aqueous solution containing the substrate N-acetyltyrosine ethyl ester exhibited Langmuir-type binding of the substrate. Its binding constant of 6.1 × 104 M−1 was about 20 times larger than that observed for a monolayer prepared on pure water. The behavior may have arisen from a substrate-induced rearrangement of the four kinds of polypeptides in the monolayer, forming a substrate-binding structure similar to that found in serine protease. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2186–2191, 2000