Sanghera, Narinder and Pinheiro, Teresa J. T. (2000) Unfolding and refolding of cytochrome c driven by the interaction with lipid micelles. Protein Science, Vol.9 (No.6). pp. 1194-1202. doi:10.1110/ps.9.6.1194 ISSN 1194-1202.

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Abstract

Binding of native cyt c to L-PG micelles leads to a partially unfolded conformation of cyt c. This micelle-bound state has no stable tertiary structure, but remains as -helical as native cyt c in solution. In contrast, binding of the acid-unfolded cyt c to L-PG micelles induces folding of the polypeptide, resulting in a similar helical state to that originated from the binding of native cyt c to L-PG micelles. Far-ultraviolet (UV) circular dichroism (CD) spectra showed that this common micelle-associated helical state (HL) has a native-like -helix content, but is highly expanded without a tightly packed hydrophobic core, as revealed by tryptophan fluorescence, near-UV, and Soret CD spectroscopy. The kinetics of the interaction of native and acid-unfolded cyt c was investigated by stopped-flow tryptophan fluorescence. Formation of HL from the native state requires the disruption of the tightly packed hydrophobic core in the native protein. This micelle-induced unfolding of cyt c occurs at a rate 0.1 s1, which is remarkably faster in the lipid environment compared with the expected rate of unfolding in solution. Refolding of acid-unfolded cyt c with L-PG micelles involves an early highly helical collapsed state formed during the burst phase (<3 ms), and the observed main kinetic event reports on the opening of this early compact intermediate prior to insertion into the lipid micelle.

Item Type:	Journal Article
Subjects:	Q Science > QR Microbiology
Divisions:	Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) > Biological Sciences ( -2010)
Library of Congress Subject Headings (LCSH):	Cytochrome c, Lipid membranes, Micelles, Electron transport, Chemical kinetics
Journal or Publication Title:	Protein Science
Publisher:	Canbridge University Press
ISSN:	1194-1202
Official Date:	June 2000
Dates:	Date Event June 2000 Published
Volume:	Vol.9
Number:	No.6
Page Range:	pp. 1194-1202
DOI:	10.1110/ps.9.6.1194
Status:	Peer Reviewed
Access rights to Published version:	Open Access (Creative Commons)
Funder:	Royal Society (Great Britain), Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC)
Grant number:	88/B09547 (BBSRC)

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