Changes of protein folding pathways by circular permutation. Overlapping nuclei promote global cooperativity.
The evolved properties of proteins are not limited to structure and stability but also include their propensity to undergo local conformational changes. The latter, dynamic property is related to structural cooperativity and is controlled by the folding-energy landscape. Here we demonstrate that the structural cooperativity of the ribosomal protein S6 is optimized by geometric overlap of two competing folding nuclei: they both include the central beta-strand 1. In this way, folding of one nucleus catalyzes the formation of the other, contributing to make the folding transition more concerted overall. The experimental evidence is provided by an extended set of circular permutations of S6 that allows quantitative analysis of pathway plasticity at the level of individual side chains. Because similar overlap between competing nuclei also has been discerned in other proteins, we hypothesize that the coupling of several small nuclei into extended "supernuclei" represents a general principle for propagating folding cooperativity across large structural distances.
Haglund
Ellinor
E
Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, S-106 91 Stockholm, Sweden.
Lindberg
Magnus O
MO
Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, S-106 91 Stockholm, Sweden.
Oliveberg
Mikael
M
Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, S-106 91 Stockholm, Sweden. Electronic address: mikael.oliveberg@dbb.su.se.
D000818:Animals; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D017510:Protein Folding; D017433:Protein Structure, Secondary / Q000235:genetics; D038601:Ribosomal Protein S6 / Q000737:chemistry* / Q000235:genetics
D038601:Ribosomal Protein S6