Interhelical carbon bridging of catalytic helix–loop–helix polypeptide motifs

Abstract

Interhelically bridged polypeptides with helix–loop–helix motifs have been synthesised by self-catalysed, site-selective acylation reactions. Lysine residues in the helices have been bridged using the bifunctional N-hydroxysuccinimide ester disuccinimidyl glutarate (DSG). The helical content of the polypeptides increases upon bridging and the structures of the bridged peptides have been shown to have increased thermal stability. The bridging also causes increased polypeptide catalytic activity in ester hydrolysis in aqueous solution. The catalysis of the site-selective reaction has been investigated in detail using a number of designed helix–loop–helix polypeptide motifs that have been reacted with DSG and the longer N-hydroxysuccinimide ester bis(sulfosuccinimidyl) suberate (BS³). The bridging of the polypeptide PE42Dcap with DSG has been optimised and the best yield was given at pH 4.1 in 5 vol% 2,2,2-trifluoroethanol (TFE).