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Rankin SE , Watts A , Roder H , Pinheiro TJT
Folding of apocytochrome c induced by the interaction with negatively charged lipid micelles proceeds via a collapsed intermediate state
Protein Science. 1999 Feb;8(2) :381-393
PMID: ISI:000078483800013   
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Unfolded apocytochrome c acquires an alpha-helical conformation upon interaction with lipid. Folding kinetic results below and above the lipid's CMC, together with energy transfer measurements of lipid bound states, and salt-induced compact states in solution, show that the folding transition of apocytochrome c from the unfolded state in solution to a lipid- inserted helical conformation proceeds via a collapsed intermediate state (I-C). This initial compact state is driven by a hydrophobic collapse of the polypeptide chain in the absence of the heme group and may represent a hems-free analogue of an early compact intermediate detected on the folding pathway of cytochrome c in solution. Insertion into the lipid phase occurs via an unfolding step of I-C through a more extended state associated with the membrane surface (I-S). While I-C appears to be as compact as salt-induced compact states in solution with substantial alpha-helix content, the final lipid-inserted state (H-mic) is as compact as the unfolded state in solution at pH 5 and has an alpha-helix content which resembles that of native cytochrome c.
Times Cited: 5 English Article 164VG PROTEIN SCI