Theoretical determination of the CD of proteins containing closely packed antiparallel β‐sheets

Abstract

AbstractProteins containing two closely packed β‐sheets comprise an important class of biopolymers. Rotational and dipole strengths have been determined by the excition coupling model for interacting pairs of two idealized flat β‐sheets and for the double β‐sheets of seven globular proteins: plastocyanin, human prealbumin, immunoglobulin VREI, concanavalin A, Cu,Zn superoxide dismutase, staphylococcal nuclease, and elastase. The effects of various geometrical factors on the CD spectra were investigated. Results for the idealized sheets indicate that two sheets display through‐space interactions that are large at distances of 5–7 Å and remain significant even at distances typical of the intersheet separations in globular proteins (12–15 Å). The CD spectra are sensitive to the angle (Ω) between the strand directions of the two sheets, with maximum intersheet contributions at Ω = ±45°. Both the intrastrand and interstrand twisting were determined in the seven proteins, and their effects on the calculated CD are discussed. This work represents the first theoretical CD study on the interactions of two regular protein secondary structures, including rotational strength calculations on large sections (up to 135 residues) of globular proteins.