Protein prosthesis: β-peptides as reverse-turn surrogates

Authors

  • Ulrich Arnold,

    1. Institute of Biochemistry and Biotechnology, Martin-Luther University Halle-Wittenberg, 06120 Halle, Germany
    2. Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
    Search for more papers by this author
  • Bayard R. Huck,

    1. Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
    Search for more papers by this author
  • Samuel H. Gellman,

    1. Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
    Search for more papers by this author
  • Ronald T. Raines

    Corresponding author
    1. Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
    2. Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
    • Department of Biochemistry, University of Wisconsin–Madison, 433 Babcock Drive, Madison, WI 53706-1544
    Search for more papers by this author

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.

Ancillary