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>Influence of site-directed mutation of cytochrome b_5 Phe35 on the protein's structure and properties
Influence of site-directed mutation of cytochrome b_5 Phe35 on the protein's structure and properties
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Kinetic studies of the heme dissociation from the wild type and Phe35Tyr, Phe35Leu mutants of bovine liver microsomal ferricytochrome b 5 indicate that the oxidized Phe35Tyr mutant is more stable towards denaturant than wild type but Phe35Leu mutant proceeded with a different mechanism compared with wild type cytochrome b 5 and Phe35Tyr mutant protein. Because of the decrease of side chain volume in Phe35Leu mutant, a cavity produced in the interior of the protein may offer a channel for urea molecule to enter the hydrophobic pocket. When urea concentration is larger than 5 mol/L, the urea molecule may compete to coordinate the iron of heme with His39, that results in sharp increase of the rate of heme dissociation. The interaction between cytochrome b 5 and cytochrom c demonstrated that a 1:1 protein complex was formed between the two proteins. The binding constants of cytochrome b 5 with cytochrome c are: wild type K A=4.2(±0.01)×10 6(mol/L) -1 , Phe35Tyr K A=3.7(±0.01)×10 6(mol/L) -1 and Phe35Leu K A=4.7(±0.01)×10 6(mol/L) -1 respectively ( I =1 m mol/L, pH 7.0 soldium phosphate buffer, 25℃). These results clearly show that the mutation at Phe35 has no influence on the binding of cytochrome b 5 with cytochrome c and that the hydrophilic patch residues are not involved in the binding of cytochrome b 5 and cytochrome c.
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机译:Structure Determination and Mechanistic Insights of: I.Cyanobacteriochrome NpR6012g4 Light Sensor Protein in Phototaxis II.Retinal Degeneration 3 (RD3) Protein in Vision III.Ryanodine Receptor 2 (RyR2) Regulation by Calmodulin (CaM) in Cardiac Function =结构测定和机理洞悉:I.趋光性中的蓝细菌色素NpR6012g4光敏蛋白 II.视觉作用中的视网膜退化蛋白3 III.心脏功能中的钙调蛋白调控兰诺定受体2