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首页> 外文期刊>Biochemistry >Implication for using heme methyl hyperfine shifts as indicators of heme seating as related to stereoselectivity in the catabolism of heme by heme oxygenase: In-plane heme versus axial his rotation
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Implication for using heme methyl hyperfine shifts as indicators of heme seating as related to stereoselectivity in the catabolism of heme by heme oxygenase: In-plane heme versus axial his rotation

机译：使用血红素甲基超微细位移作为血红素就位指示剂的含义与血红素加氧酶分解血红素的立体选择性有关：面内血红素与轴向旋转

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摘要

The triple mutant of the solubilized, 265-residue construct of human heme oxygenase, K18E/ E29K/R183E-hHO, has been shown to redirect the exclusive alpha-regioselectivity of wild-type hHO to primarily beta,delta-selectivity in the cleavage of heme (Wang, J., Evans, J. P., Ogura, H., La Mar, G. N., and Ortiz de Montellano, P. R. (2006) Biochemistry 45, 61-73). The H-1 NMR hyperfine shift pattern for the substrate and axial His C beta H's and the substrate-protein contacts of the cyanide-inhibited protohemin and 2,4-dimethyldeuterohemin complexes of the triple mutant have been analyzed in detail,and compared to data for the WT complex. It is shown that protein contacts for the major solution isomers for both substrates in the mutant dictate similar to 90 degrees in-plane clockwise rotation relative to that in the WT. The conventional interpretation of the pattern of substrate methyl hyperfine shifts, however, indicates substrate rotations of only similar to 50 degrees. This paradox is resolved by demonstrating that the axial His25 imidazole ring also rotates counterclockwise with respect to the protein matrix in the mutant relative to that in the WT. The axial His25 C beta H hyperfine shifts are shown to serve as independent probes of the imidazole plane orientation relative to the protein matrix. The analysis indicates that the pattern of heme methyl hyperfine shifts cannot be used alone to determine the in-plane orientation of the substrate as it relates to the stereospecificity of heme cleavage, without explicit consideration of the orientation of the axial His imidazole plane relative to the protein matrix.
机译：已显示，人血红素加氧酶的265个残基可溶解的三重突变体K18E / E29K / R183E-hHO可将野生型hHO的排他性α-区域选择性重新定向到β-δ选择性切割中。血红素（Wang，J.，Evans，JP，Ogura，H.，La Mar，GN，和Ortiz de Montellano，PR（2006）Biochemistry 45，61-73）。详细分析了三重突变体的底物和轴向His C beta H的H-1 NMR超精细位移图样以及氰化物抑制的原血红素和2,4-二甲基氘血红素复合物的底物-蛋白质接触WT复合体。结果表明，突变体中两种底物的主要溶液异构体的蛋白质接触决定了相对于WT而言，其平面顺时针旋转角度为90度。然而，对底物甲基超细位移的图案的常规解释表明，底物旋转仅类似于50度。通过证明轴向His25咪唑环相对于突变体中的蛋白质基质相对于WT中的蛋白质基质也逆时针旋转来解决该矛盾。轴向His25 CβH超精细位移显示为相对于蛋白质基质的咪唑平面取向的独立探针。分析表明，血红素甲基超细位移的模式不能单独用于确定底物的平面内方向，因为它与血红素裂解的立体特异性有关，而没有明确考虑轴向His咪唑平面相对于HIM的方向。蛋白质基质。

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