A Distal Pocket Leu Residue Inhibits the Binding of O2 and NO at the Distal Heme Site of Cytochrome c

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• 作者：Elizabeth M. Garton ; David A. Pixton ; Christine A. Petersen ; Robert R. Eady ; S. Samar Hasnain ; and Colin R. Andrew
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：January 25, 2012
• 年：2012
• 卷：134
• 期：3
• 页码：1461-1463
• 全文大小：190K
• 年卷期：v.134,no.3(January 25, 2012)
• ISSN：1520-5126

文摘

Cytochromes c鈥?are pentacoordinate heme proteins with sterically hindered distal sites that bind NO and CO but do not form stable complexes with O₂. Removal of distal pocket steric hindrance via a Leu鈫扐la mutation yields favorable O₂ binding (K_d 49 nM) without apparent H-bond stabilization of the Fe鈥揙₂ moiety, as well as an extremely high distal heme-NO affinity (K_d 70 fM). The native Leu residue inhibits distal coordination of diatomic ligands by decreasing k_on as well as increasing k_off. The connection between distal steric constraints, k_off values, and distal to proximal heme-NO conversion is discussed.