NMR studies of a viral protein that mimics the regulators of complement activation.

摘要: Abstract Vaccinia virus complement control protein (VCP) is a 243-residue that similar in sequence to the regulators of activation; its role defend against attack by host system. A fragment this spanning two (CP)-modules (residues 126 243) which make up C-terminal half VCP has been expressed Pichia pastoris . 15 N-labelled sample was purified for purposes structure determination and measurements dynamics solution using NMR. Structures were calculated on basis 1767 NMR-derived distance angle restraints, with longer than normal high-temperature simulated annealing (SA) protocol improved convergence. The viral CP-modules are structurally very 15th 16th human factor H (fH; average r.m.s.d., invariant Trp Cys, four pair-wise comparisons,=1.2 A) but less fifth CP-module fH (average r.m.s.d.=2.2 A). In fragment, orientation one module respect other clearly defined experimental data, T 1 consistent only limited flexibility at module-module interface. r.m.s.d. over all 118 residues (backbone atoms) 0.73 A. intermodular better than, significantly different from, observed pair from (re-calculated extended SA protocol). long axis second tilted 59(±4)° first (50(±13)° pair), twisted 22(±6)° (223(±17)° fH). differences between proteins may be rationalised terms lack hydrogen-bond stabilised secondary N-terminal portion 16, number type amino acid side-chains interface predicted third fourth C4 binding and, probably, modules guinea pig acrosomal matrix 67; formulation general rules predicting interfaces awaits further data.