Characterisation of low free-energy excited states of folded proteins

Citation
Nj. Baxter et al., Characterisation of low free-energy excited states of folded proteins, J MOL BIOL, 284(5), 1998, pp. 1625-1639
Citations number
47
Categorie Soggetti
Molecular Biology & Genetics
Journal title
JOURNAL OF MOLECULAR BIOLOGY
ISSN journal
00222836 → ACNP
Volume
284
Issue
5
Year of publication
1998
Pages
1625 - 1639
Database
ISI
SICI code
0022-2836(199812)284:5<1625:COLFES>2.0.ZU;2-H
Abstract
It is demonstrated that the identity of residues accessing excited conforma tional states that ape of low free energy relative to the ground state in p roteins can be obtained from amide proton NMR chemical shift temperature de pendences displaying significant curvature. For the N-terminal domain of ph osphoglycerate kinase, hen egg-white lysozyme and BPTI, conformational hete rogeneity arises from a number of independent sources, including: structura l instability resulting from deletion of part of the protein; a minor confo rmer generated through disulphide bond iso merisation; an alternative hydro gen bond network associated with buried water molecules; alternative hydrog en bonds involving backbone amides and surface-exposed side-chain hydrogen bond accepters; and the disruption of loops, ends of secondary structural e lements and chain termini. in many of these cases, the conformational heter ogeneity at these sites has previously been identified by X-ray and/or NMR studies, but conformational heterogeneity of buried water molecules has hit herto received little attention. These multiple independent low free-energy excited states each involve a small number of residues and are shown to be within 2.5 kcal mol(-1) of the ground state. Their relationship with the p artially unfolded forms previously characterised using amide proton exchang e studies is discussed. (C) 1998 Academic Press.