Structure and dynamics of lipid-associated states of apocytochrome c.
Apocytochrome c (apocyt c), which in aqueous solution is largely unstructured, acquires an alpha-helical conformation upon association with lipid membranes. The extent of alpha-helix induced in apocyt c is lipid-dependent and this folding process is driven by both electrostatic and hydrophobic lipid-protein interactions. The structural and dynamic properties of apocyt c in lipid membranes were investigated by attenuated total reflection Fourier transform infrared spectroscopy combined with amide H-D exchange kinetics. Apocyt c acquires a higher content of alpha-helical structure with negatively charged membranes than with zwitterionic ones. For all membranes studied here, the helices of these partially folded states of apocyt c have a preferential orientation perpendicular to the plane of the lipid membrane. The H-D exchange revealed that a small fraction of amide protons of apocyt c, possibly associated with a stable folded domain protected by the lipid, remained protected from exchange over 20 min. However, a large fraction of amide protons exchanged in less than 20 min, indicating that the helical states of apocyt c in lipid membranes are very dynamic.
Bryson
E A
EA
Department of Biological Sciences, University of Warwick, Coventry, UK.
Rankin
S E
SE
Goormaghtigh
E
E
Ruysschaert
J M
JM
Watts
A
A
Pinheiro
T J
TJ
D001059:Apoproteins / Q000737:chemistry*; D003574:Cytochrome c Group / Q000737:chemistry*; D045304:Cytochromes c; D007700:Kinetics; D008055:Lipids / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017550:Spectroscopy, Fourier Transform Infrared
D001059:Apoproteins; D003574:Cytochrome c Group; D008055:Lipids; D045304:Cytochromes c