Title | Redox Capacity of an Extracellular Matrix Protein Associated with Adhesion in Mytilus californianus. |
Publication Type | Journal Article |
Year of Publication | 2016 |
Authors | Nicklisch, SCT, Spahn, JE, Zhou, H, Gruian, CM, Waite, JH |
Journal | Biochemistry |
Volume | 55 |
Issue | 13 |
Pagination | 2022-30 |
Date Published | 2016 Apr 5 |
ISSN | 1520-4995 |
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. |
DOI | 10.1021/acs.biochem.6b00044 |
Alternate Journal | Biochemistry |
PubMed ID | 26998552 |