Accessibility of folding mutation sites in the native phage p22 tailspike protein trimer

Abstract

Cystein substitutions at sites of 3 temperature-sensitive-folding (tsf) and 2 tsf-suppressor mutations in the phage P22 tailspike protein were created in order to probe the solvent accessibility of these sites. Cysteines at 2 tsf sites (residues 235 and 244) reacted readily with Ellman's reagent and labeled by fluorescent maleimides. Spectra of the labeled proteins indicated the electrostatic enviornment of the 2 sites to be different. The 2 suppressor sites (residues 331 and 334) and residue 238 were inaccessible to the reagents.