A mussel polyphenol oxidase-like protein shows thiol-mediated antioxidant activity

Abstract

Marine mussels adhere underwater to a variety of substrates using adhesive proteins with post-translationally modified amino acids, such as 3,4-dihydroxyphenylalanine (DOPA) residues, as a key chemical signature. DOPA can auto-oxidize easily in seawater reducing the adhesion strength, but contributing to subsequent cohesion (cross-linking) of the underlying proteins. To maintain both reduced and oxidized forms of DOPA with corresponding adhesion and cohesion properties, strict redox regulation is necessary for mussel underwater adhesion. In this study, a full-length polyphenol oxidase-like protein (PPOL) from Mytilus galloprovincialis was identified after screening of a mussel foot cDNA library using different degenerated PCR primers. The recombinant PPOL (rPPOL) was successfully produced in Escherichia coli. The rPPOL exhibits thiol-dependent antioxidant activity suppressing DOPA oxidation. This finding provides insights into how DOPA chemistry could be regulated and presumably inspires future applications of DOPA-mediated adhesion materials.