title: The bacteriohemerythrin from Methylococcus capsulatus (Bath): Crystal structures reveal that Leu114 regulates a water tunnel.
abstract: The bacteriohemerythrin (McHr) from Methylococcus capsulatus (Bath) is an oxygen carrier that serves as a transporter to deliver O2 from the cytosol of the bacterial cell body to the particulate methane monooxygenase residing in the intracytoplasmic membranes for methane oxidation. Here we report X-ray protein crystal structures of the recombinant wild type (WT) McHr and its L114A, L114Y and L114F mutants. The structure of the WT reveals a possible water tunnel in the McHr that might be linked to its faster autoxidation relative to hemerythrin in marine invertebrates. With Leu114 positioned at the end of this putative water tunnel, the hydrophobic side chain of this residue seems to play a prominent role in controlling the access of the water molecule required for autoxidation. This hypothesis is examined by comparing the autoxidation rates of the WT McHr with those of the L114A, L114Y and L114F mutants. The biochemical data are correlated with structural insights derived from the analysis of the putative water tunnels in the various McHr proteins provided by the X-ray structures.
authors.affiliation: Department of Applied Chemistry, National Pingtung University, Pingtung 90003, Taiwan. Electronic address: kelvin@mail.nptu.edu.tw.
authors.forename: Kelvin H-C
authors.initials: KH
authors.lastname: Chen
authors.affiliation: Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, 30076 Hsinchu, Taiwan.
authors.forename: Phimonphan
authors.initials: P
authors.lastname: Chuankhayan
authors.affiliation: Department of Applied Chemistry, National Pingtung University, Pingtung 90003, Taiwan; Institute of Bioinformatics and Structural Biology and Structural Biology Program, National Tsing Hua University, Hsinchu 30014, Taiwan.
authors.forename: Hsin-Hui
authors.initials: HH
authors.lastname: Wu
authors.affiliation: Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, 30076 Hsinchu, Taiwan; Department of Biotechnology and Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan; Department of Physics, National Tsing Hua University, Hsinchu 30014, Taiwan. Electronic address: cjchen@nsrrc.org.tw.
authors.forename: Chun-Jung
authors.initials: CJ
authors.lastname: Chen
authors.affiliation: Computer Chemistry Laboratory, Hyogo University of Teacher Education, 673-1494 Hyogo, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Steve S-F
authors.initials: SS
authors.lastname: Yu
authors.affiliation: Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Sunney I
authors.initials: SI
authors.lastname: Chan
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006422:Hemerythrin / Q000737:chemistry*; D007501:Iron; D007930:Leucine / Q000737:chemistry*; D020619:Methylococcus capsulatus / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D006422:Hemerythrin; D011994:Recombinant Proteins; D014867:Water; D007501:Iron; D007930:Leucine; D010100:Oxygen
keywords: Autoxidation; Bacteriohemerythrin; Methylococcus capsulatus (Bath); Oxygen carrier protein; Water tunnel