Protein Science 2013-03-01

Protein prosthesis: β-peptides as reverse-turn surrogates.

Ulrich Arnold, Bayard R Huck, Samuel H Gellman, Ronald T Raines

Index: Protein Sci. 22(3) , 274-9, (2013)

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Abstract

The introduction of non-natural modules could provide unprecedented control over folding/unfolding behavior, conformational stability, and biological function of proteins. Success requires the interrogation of candidate modules in natural contexts. Here, expressed protein ligation is used to replace a reverse turn in bovine pancreatic ribonuclease (RNase A) with a synthetic β-dipeptide: β²-homoalanine-β³-homoalanine. This segment is known to adopt an unnatural reverse-turn conformation that contains a 10-membered ring hydrogen bond, but one with a donor-acceptor pattern opposite to that in the 10-membered rings of natural reverse turns. The RNase A variant has intact enzymatic activity, but unfolds more quickly and has diminished conformational stability relative to native RNase A. These data indicate that hydrogen-bonding pattern merits careful consideration in the selection of beneficial reverse-turn surrogates.Copyright © 2012 The Protein Society.