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

Abstract

SynopsisProteins containing two closely packed /3-sheets comprise an important class of biopolymers. Rotational and dipole strengths have been determined by the exciton coupling model for interacting pairs of two idealized flat /%sheets and for the double /3-sheets of seven globular proteins: plastocyanin, human prealbumin, immunoglobulin V,,, , 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 A and remain significant even at distances typical of the intersheet separations in globular proteins (12-15 A). The CD spectra are sensitive to the angle (Q) between the strand directions of the two sheets, with maximum intersheet contributions at Cl = k 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.

Asparagine deamidation in recombinant human lymphotoxin: Hindrance by three-dimensional structures

“…In the absence of Gdn HCl, the CD spectrum of the native rhLT had a negative signal at 223 nm and a strong positive signal at around 205 nm and below. This CD spectrum is characteristic of those for highly twisted b-sheet secondary structures, [10][11][12] and was consistent with the X-ray crystal structure. 8 The negative ellipticity around 223 nm appeared of low intensity, which may have resulted from positive intensity contribution from Trp residues.…”

The β Sheet ⇌ Coil Transition of Polypeptides, as Determined by Circular Dichroism

“…They also depend on the precise values of the torsion angles <!> and tjJ used in the construction of the individual strands (Applequist, 1982). Intersheet interaction can be expected to affect the CD in closely packed 13 sheets, and the effect depends on the angle between the interacting 13 sheets (Manning and Woody, 1987;Manning et al, 1988). Further variations in the CD spectra are possible when the 13 sheets are oriented, but here we will restrict ourselves to the types of measurements that might be performed in dilute solution, where the system as a whole is isotropic.…”

WW: An isolated three‐stranded antiparallel β‐sheet domain that unfolds and refolds reversibly; evidence for a structured hydrophobic cluster in urea and GdnHCl and a disordered thermal unfolded state

“…The native WW far-UV CD spectrum is characterized by two peaks, a small absorption with a positive ellipticity centered around 230 nm and an intense negative peak at 202 nm. The spectrum does not exhibit the classical b-sheet signal designated by a negative peak at 217-218 nm and a positive peak at 195-197 nm Woody, 1985Woody, , 1987Woody, , 1993Manning & Woody, 1987! but more closely resembles the signal of an ensemble of less-ordered states Fasman, 1996!.…”