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Proline-40 is Essential to Maintaining Cytochrome b_5's Stability and Its Electron Transfer with Cytochrome c
作者姓名:王志强  邬建  王韵华  钱雯  谢毅  夏宗芗  黄仲贤
作者单位:WANG,Zhi-Qiang ⊥,a WU,Jian ⊥,c WANG,Yun-Hua a QIAN,Wen a XIE,Yi b XIA,Zong-Xiang,c HUANG,Zhong-Xian,a a Chemical Biology Laboratory,Chemistry Department,Fudan University,Shanghai 200433,China b National
基金项目:theNationalNaturalScienceFoundationofChina (Nos.39990 6 0 0and 2 0 0 710 0 9) ,andtheStateKeyLaborato riesofGeneticEngineeringofSchoolofLifeScienceofFudanUniversity
摘    要:IntroductionCytochromeb5(Cytb5)isamembrane boundpro tein .Itcanbeproteolyzedtoyieldasoluble ,hydrophilicdomaincontaininganon covalentlyboundhemegroup .Cytb5isinvolvedinelectrontransferwithavarietyofproteins,suchascytochromec (Cytc) ,1 3 metmyo globin ,2 methemoglo…


Proline-40 is Essential to Maintaining Cytochrome b_5's Stability and Its Electron Transfer with Cytochrome c
Zhi‐Qian Wang,Jian Wu,Yun‐Hua Wang,Wen Qian,Yi Xie,Zong‐Xiang Xia,Zhong‐Xian Huang.Proline-40 is Essential to Maintaining Cytochrome b_5''''s Stability and Its Electron Transfer with Cytochrome c[J].Chinese Journal of Chemistry,2002,20(11):1212-1224.
Authors:Zhi‐Qian Wang  Jian Wu  Yun‐Hua Wang  Wen Qian  Yi Xie  Zong‐Xiang Xia  Zhong‐Xian Huang
Abstract:In order to illustrate the roles played by Pro40 in the structure, properties and functions of Cytochrome b5, three mutated genes, P40V, P40Y, P40G were constructed in this work. Only the P40V gene was successfully expressed into holoprotein in E. coli JM83. According to the results of X‐ray crystallographic analysis and various kinds of spectroscopy studies, it is evident that substituting valine for Pro40 does not result in significant alterations in the protein′s overall structure; however, local conformational perturbations in the proximity of the heme do occur. The redox potential of the P40V mutant is 40 mV lower than that of the wild type protein. Its stability towards heat, urea, acid and ethanol were significantly decreased. The mutation leads to a decrease in the hydrophobicity of the heme pocket, which is probably the major factor contributing to the above changes. Binding constants and electron transfer rates between cytochrome bs and cytochrome c were determined using UV‐visible spectroscopy and stopped‐flow techniques for both the wild type and the mutant. The results showed that the substitution of Pro40 by valine does not influence the binding constant of cytochrome b5 to cytochrome c; however, the electron transfer rate between them decreased significantly. This indicates that proline‐40 is essential to maintaining cytochrome bss stability and its electron transfer with cytochrome c. These studies also provided a good example that property and functional changes of a protein do not necessarily require large overall structural alterations; in most cases, only perturbations on the local conformations are sufficient to induce significant changes in protein′s properties and functions.
Keywords:cytochrome b  5  mutation  stability  function  X-ray structure analysis
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