ION BINDING TO CYTOCHROME-C STUDIED BY NUCLEAR MAGNETIC QUADRUPOLE RELAXATION

被引:32
作者
ANDERSSON, T
THULIN, E
FORSEN, S
机构
[1] From the Department of Physical Chemistry 2, University of Lund, Chemical Center, Lund
[2] the European Conference on NMR of Macromolecules, Sassari
关键词
D O I
10.1021/bi00579a008
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The enhancement of the 35Cl- transverse relaxation rate on binding of chloride ions to oxidized and reduced cytochrome c has been studied under conditions of variable sodium chloride concentration, temperature, pH, sodium phosphate, iron hexacyanide and sodium cyanide concentration. The results revealed the presence of a strong binding site(s) for chloride in both oxidized and reduced cyt c, with a higher affinity in ferrocytochrome c. Competition experiments suggest that these sites also bind iron hexacyanide and phosphate. Cyanide binding to the iron in ferricytochrome c at alkaline and neutral pH was shown to decrease the binding of chloride. The pH dependence of the 35Cl- relaxation rate has been fitted by using literature pK values for ionizable groups. No indications of Na+ binding to oxidized and reduced cytochrome c have been observed by using 23Na+ NMR. Our results suggest that chloride is bound near the exposed heme edge and that the surface structure or dynamics in this region are different in the two oxidation states. © 1979, American Chemical Society. All rights reserved.
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页码:2487 / 2493
页数:7
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