Ab initio quantum mechanical study of metal substitution in analogues of rubredoxin: Implications for redox potential control

被引:9
作者
Beck, BW [1 ]
Koerner, JB [1 ]
Ichiye, T [1 ]
机构
[1] Washington State Univ, Dept Biochem Biophys, Pullman, WA 99164 USA
关键词
D O I
10.1021/jp9912814
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Substitution of different metals into the redox sites of metalloproteins is a means of studying the structure of the native protein and of varying the redox properties of the protein. The implicit assumption is often made that metal substitution changes only intrinsic properties of the redox site such as the ionization potential without altering the surrounding protein or solvent. However, if this is not true, structural studies of metal-substituted proteins will not reflect the native protein and the differences in redox potential upon metal substitution will not be simply the differences in ionization potential of the redox sites because of perturbations in the extrinsic electric field. Here, we present an ab initio unrestricted Hartree-Fock quantum mechanical study of metal substitution in the [M(SCH3)(4))(2-/1-) analogue, where M = Fe, Co, Ni, and Zn, of the protein rubredoxin. Variations in several physical properties were determined and compared to experimental data. Upon metal substitution, only minor variations in geometry, atomic spin, and atom-centered partial charges of the redox site are observed. However, significant variation is found in the energies of reduction, on the order of 100-1000 mV. This indicates that when such substitutions are made into an Fe-S metalloprotein, little change will occur in the interactions between the metal site and the surrounding protein and thus the surrounding protein structure and the resultant electric field will not change. Thus, the structure is relevant to the native protein and the redox properties are mainly determined by the variations in the intrinsic ionization potential of the metal site and not the extrinsic field of the surrounding protein and solvent.
引用
收藏
页码:8006 / 8015
页数:10
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