Chameleonicity and folding of the C-fragment of TOP7

¹ Wayne County Community College District - Detroit, MI 48226, USA
² Department of Physics, Michigan Technological University - Houghton, MI 49931, USA
³ Department of Chemistry & Biochemistry, University of Oklahoma - Norman, OK 73019, USA

^a mlgaye@mtu.edu
^b cehardwi@mtu.edu
^c mkouza@mtu.edu
^d uhansmann@ou.edu

Received: 6 December 2011
Accepted: 14 February 2012

Abstract

Using a specifically designed Go-model we have performed all-atom simulations of the C-fragment of TOP7. Our results support previous results (see Mohanty S. et al., Proc. Natl. Acad. Sci. U.S.A., 105 (2008) 8004; Mohanty S. and Hansmann U. H. E., J. Phys. Chem. B, 112 (2008) 15134) that indicate folding of this protein through configurations with non-native secondary structure. The N-terminal residues form first an extension of a subsequent α-helix, before finally refolding into a β-strand that completes a three-stranded β-sheet in the final structure. We show that mutations which reduce the “chameleonicity” of N-terminal residues (by increasing the propensity for “strandness” and reducing that for “helicity”) lead to folding into the same structure but with reduced folding rates and larger free-energy barriers.