title: Tough coating proteins: subtle sequence variation modulates cohesion.
abstract: Mussel foot protein-1 (mfp-1) is an essential constituent of the protective cuticle covering all exposed portions of the byssus (plaque and the thread) that marine mussels use to attach to intertidal rocks. The reversible complexation of Fe(3+) by the 3,4-dihydroxyphenylalanine (Dopa) side chains in mfp-1 in Mytilus californianus cuticle is responsible for its high extensibility (120%) as well as its stiffness (2 GPa) due to the formation of sacrificial bonds that help to dissipate energy and avoid accumulation of stresses in the material. We have investigated the interactions between Fe(3+) and mfp-1 from two mussel species, M. californianus (Mc) and M. edulis (Me), using both surface sensitive and solution phase techniques. Our results show that although mfp-1 homologues from both species bind Fe(3+), mfp-1 (Mc) contains Dopa with two distinct Fe(3+)-binding tendencies and prefers to form intramolecular complexes with Fe(3+). In contrast, mfp-1 (Me) is better adapted to intermolecular Fe(3+) binding by Dopa. Addition of Fe(3+) did not significantly increase the cohesion energy between the mfp-1 (Mc) films at pH 5.5. However, iron appears to stabilize the cohesive bridging of mfp-1 (Mc) films at the physiologically relevant pH of 7.5, where most other mfps lose their ability to adhere reversibly. Understanding the molecular mechanisms underpinning the capacity of M. californianus cuticle to withstand twice the strain of M. edulis cuticle is important for engineering of tunable strain tolerant composite coatings for biomedical applications.
authors.affiliation: Department of Chemical Engineering, ‡Biomolecular Science and Engineering, §Department of Molecular, Cell and Developmental Biology, ∥Department of Chemistry and Biochemistry, and #Materials Research Laboratory, University of California , Santa Barbara, California 93106, United States.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Das
authors.forename: Dusty R
authors.initials: DR
authors.lastname: Miller
authors.forename: Yair
authors.initials: Y
authors.lastname: Kaufman
authors.forename: Nadine R
authors.initials: NR
authors.lastname: Martinez Rodriguez
authors.forename: Alessia
authors.initials: A
authors.lastname: Pallaoro
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Harrington
authors.forename: Maryte
authors.initials: M
authors.lastname: Gylys
authors.forename: Jacob N
authors.initials: JN
authors.lastname: Israelachvili
authors.forename: J Herbert
authors.initials: JH
authors.lastname: Waite
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D049878:Mytilus / Q000737:chemistry; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry*
chemical_list: D011506:Proteins; D007501:Iron