title: The conformational changes of apocytochrome c upon binding to phospholipid vesicles and micelles of phospholipid based detergents: a circular dichroism study.
abstract: The influence of lipid aggregates on the secondary structure of the mitochondrial precursor protein apocytochrome c was investigated by circular dichroism techniques. A conformational change of the protein from a random coil to partially alpha-helical structures was observed upon binding to negatively charged DOPS SUVs. Also DOPC SUVs showed to induce such a conformational change, but to a lesser extent. The detergents decyl-, lauryl and myristoyl-phosphoglycol or -phosphocholine, were synthesized as micel forming phospholipid analogs and are shown to mimic the phospholipids well in their ability to induce alpha-helices in the protein. A full assignment of the regions where the possible alpha-helices are formed is proposed by making use of derived fragments of apocytochrome c, prediction methods and the known X-ray structure of cytochrome c. Besides a helix at the N-terminus (residues 1-22) and at the C-terminal part (residues 80-101), two regions in the middle section (residues 49-54 and 59-70) are suggested to be helical. It is inferred that the two cysteines in the positions 14 an 17 at the N-terminal part are facing in the same direction, which could facilitate the covalent attachment of the heme group to the precursor in the translocation process.
authors.affiliation: Centre for Biomembranes and Lipid Enzymology, State University Utrecht, The Netherlands.
authors.forename: H H
authors.initials: HH
authors.lastname: de Jongh
authors.forename: B
authors.initials: B
authors.lastname: de Kruijff
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry* / Q000378:metabolism; D002942:Circular Dichroism; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism; D045304:Cytochromes c; D003902:Detergents / Q000378:metabolism*; D006736:Horses; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D009206:Myocardium / Q000201:enzymology; D010743:Phospholipids / Q000378:metabolism*; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D001059:Apoproteins; D003574:Cytochrome c Group; D003902:Detergents; D008823:Micelles; D010743:Phospholipids; D045304:Cytochromes c