EFFECTS OF MANGANOUS ION ON THE P-31 NUCLEAR MAGNETIC-RESONANCE SPECTRUM OF ADENOSINE-TRIPHOSPHATE BOUND TO NITRATED G-ACTIN - PROXIMITY OF DIVALENT METAL-ION AND NUCLEOTIDE BINDING-SITES

被引:25
作者
BRAUER, M
SYKES, BD
机构
[1] UNIV ALBERTA, MRC, PROT STRUCT & FUNCT GRP, EDMONTON T6G 2H7, ALBERTA, CANADA
[2] UNIV ALBERTA, DEPT BIOCHEM, EDMONTON T6G 2H7, ALBERTA, CANADA
关键词
D O I
10.1021/bi00266a032
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
G-Actin [rabbit muscle] has 1 high-affinity binding site for ATP and 1 high-affinity binding site for divalent metal ions such as Ca2+, Mg2+ or Mn2+. 31P NMR was used to study the high-affinity ATP binding site of a relatively nonpolymerizable selectively nitrated derivative of G-actin. When paramagnetic Mn ion was added to nitrated G-actin, the line widths of the resonances for the .alpha.-, .beta.- and .gamma.-phosphates of the bound ATP did not increase substantially. The areas of the resonances of all 3 phosphates decreased with increasing concentration of Mn ion. This decrease in area paralleled a decrease in tightly bound Ca displaced by the Mn ion. Mn-induced polymerization of the nitrated G-actin was a relatively minor process in these experiments. The 31P NMR results are consistent with very slow exchange between the Ca2+.cntdot.ATP.cntdot.nitrated G-actin complex and the Mn2+.cntdot.ATP.cntdot.nitrated G-actin complex. The areas of the observed resonances, which represent the Ca2+.cntdot.ATP.cntdot.nitrated G-actin complex, vary as a function of the population of this complex, but the line widths are not affected by exchange with the Mn.cntdot.ATP.cntdot.nitrated G-actin complex. The line widths of the 31P NMR resonances of the bound ATP in the Mn.cntdot.ATP.cntdot.nitrated G-actin complex are too broad to be detected (> 400 Hz) due to the paramagnetic effect of the tightly bound Mn ion. The high-affinity metal ion binding site on G-actin (occupied by Mn ion) must be < 10 .ANG. from the ATP binding site.
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页码:5934 / 5939
页数:6
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