title: Redox Capacity of an Extracellular Matrix Protein Associated with Adhesion in Mytilus californianus.
abstract: Adhesive mussel foot proteins (Mfps) rely in part on DOPA (3,4-dihydroxyphenyl-l-alanine) side chains to mediate attachment to mineral surfaces underwater. Oxidation of DOPA to Dopaquinone (Q) effectively abolishes the adsorption of Mfps to these surfaces. The thiol-rich mussel foot protein-6 (Mfp-6) rescues adhesion compromised by adventitious DOPA oxidation by reducing Q back to DOPA. The redox chemistry and kinetics of foot-extracted Mfp-6 were investigated by using a nonspecific chromogenic probe to equilibrate with the redox pool. Foot-extracted Mfp-6 has a reducing capacity of ~17 e(-) per protein; half of this comes from the cysteine residues, whereas the other half comes from other constituents, probably a cohort of four or five nonadhesive, redox-active DOPA residues in Mfp-6 with an anodic peak potential ~500 mV lower than that for oxidation of cysteine to cystine. At higher pH, DOPA redox reversibility is lost possibly due to Q scavenging by Cys thiolates. Analysis by one- and two-dimensional proton nuclear magnetic resonance identified a pronounced β-sheet structure with a hydrophobic core in foot-extracted Mfp-6 protein. The structure endows redox-active side chains in Mfp-6, i.e., cysteine and DOPA, with significant reducing power over a broad pH range, and this power is measurably diminished in recombinant Mfp-6.
authors.affiliation: Marine Science Institute and Department of Molecular, Cell & Developmental Biology, University of California , Santa Barbara, California 93106, United States.
authors.forename: Sascha C T
authors.initials: SC
authors.lastname: Nicklisch
authors.affiliation: Marine Science Institute and Department of Molecular, Cell & Developmental Biology, University of California , Santa Barbara, California 93106, United States.
authors.forename: Jamie E
authors.initials: JE
authors.lastname: Spahn
authors.affiliation: Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106, United States.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Institute of Interdisciplinary Research in Bio-Nano-Sciences, Babeş-Bolyai University , Cluj-Napoca 400084, Romania.
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Gruian
authors.affiliation: Marine Science Institute and Department of Molecular, Cell & Developmental Biology, University of California , Santa Barbara, California 93106, United States.
authors.forename: J Herbert
authors.initials: JH
authors.lastname: Waite
mesh_terms: D000268:Adhesiveness; D000818:Animals; D016227:Benzoquinones / Q000378:metabolism; D055162:Biocatalysis; D001713:Biphenyl Compounds / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D049878:Mytilus / Q000502:physiology*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D010851:Picrates / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D001713:Biphenyl Compounds; D016326:Extracellular Matrix Proteins; D010851:Picrates; D011994:Recombinant Proteins; D004295:Dihydroxyphenylalanine; C035157:dopaquinone; C004931:1,1-diphenyl-2-picrylhydrazyl; D003545:Cysteine