Cytochrome c and SDS: a molten globule protein with altered axial ligation.
Saccharomices cerevisiae (yeast iso-1) cytochrome c has been investigated in the presence of 100 mM SDS in order to simulate the interaction of cytochrome c with membrane. Under these circumstances, a high spin species with detached methionine axial ligand is observed through NMR, in analogy to findings on the horse heart protein. However, at variance with the latter system, for the yeast protein also a low spin species is detected, which appears to be present with a concentration of about 40% with respect to that of the high spin species. The R(1), R(2), [1H]-15N NOE of backbone amides which are not affected by paramagnetism are homogeneous and allow a simultaneous analysis of the data for the two species. The result is that the rotational correlation time is larger than in water and larger than expected on the basis of viscosity of the SDS-containing solution. This finding suggests interactions of cytochrome c with SDS. Furthermore, it appears that there is subnanosecond backbone mobility, which also accounts for the decreased intensity of NOE cross-peaks and may be associated with equilibria between helical and random coil structure. The dynamic behavior appears to be a common feature of the high spin and low spin species and is consistent with the presence of a molten globule state. The molten globule nature of the protein could account for the presence of the different axial coordination of the heme iron. Such findings are meaningful with respect to the physiology of cytochrome c as electron transfer protein and as promoter of apoptosis.
Bertini
Ivano
I
CERM, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy. bertini@cerm.unifi.it
Turano
Paola
P
Vasos
Paul R
PR
Bondon
Arnaud
A
Chevance
Soizic
S
Simonneaux
Gérard
G
D000818:Animals; D045304:Cytochromes c / Q000737:chemistry*; D006736:Horses; D009682:Magnetic Resonance Spectroscopy; D009206:Myocardium / Q000737:chemistry; D011487:Protein Conformation; D011522:Protons; D012399:Rotation; D012441:Saccharomyces cerevisiae / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013997:Time Factors; D014783:Viscosity
D011522:Protons; D029701:Saccharomyces cerevisiae Proteins; D012967:Sodium Dodecyl Sulfate; D045304:Cytochromes c