期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：11
页码：2916-2921
DOI：10.1073/pnas.1617615114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In MtrF, an outer-membrane multiheme cytochrome, the 10 heme groups are arranged in heme binding domains II and IV along the pseudo- C 2 axis, forming the electron transfer (ET) pathways. Previous reports based on molecular dynamics simulations showed that the redox potential ( E m) values for the heme pairs located in symmetrical positions in domains II and IV were similar, forming bidirectional ET pathways [Breuer M, Zarzycki P, Blumberger J, Rosso KM (2012) J Am Chem Soc 134(24):9868–9871]. Here, we present the E m values of the 10 hemes in MtrF, solving the linear Poisson–Boltzmann equation and considering the protonation states of all titratable residues and heme propionic groups. In contrast to previous studies, the E m values indicated that the ET is more likely to be downhill from domain IV to II because of localization of acidic residues in domain IV. Reduction of hemes in MtrF lowered the E m values, resulting in switching to alternative downhill ET pathways that extended to the flavin binding sites. These findings present an explanation of how MtrF serves as an electron donor to extracellular substrates.
