title: Electron transfer pathways in a multiheme cytochrome MtrF.
abstract: In MtrF, an outer-membrane multiheme cytochrome, the 10 heme groups are arranged in heme binding domains II and IV along the pseudo-C2axis, forming the electron transfer (ET) pathways. Previous reports based on molecular dynamics simulations showed that the redox potential (Em) 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 Soc134(24):9868-9871]. Here, we present theEmvalues 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, theEmvalues 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 theEmvalues, 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.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8654, Japan.|Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8904, Japan.
authors.forename: Hiroshi C
authors.initials: HC
authors.lastname: Watanabe
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8654, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yamashita
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8654, Japan; hiro@appchem.t.u-tokyo.ac.jp.|Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8904, Japan.
authors.forename: Hiroshi
authors.identifier: 0000-0002-5849-8150
authors.initials: H
authors.lastname: Ishikita
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004579:Electron Transport; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D008024:Ligands; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D020592:Shewanella / Q000378:metabolism*
chemical_list: D008024:Ligands; D024101:Mitochondrial Proteins; D006418:Heme
keywords: Mtr conduit; Shewanella species; decaheme; dissimilatory metal-reducing bacteria; flavin