Protein- and metal-dependent interactions of a prominent protein in mussel adhesive plaques.
The adhesive plaques of Mytilus byssus are investigated increasingly to determine the molecular requirements for wet adhesion. Mfp-2 is the most abundant protein in the plaques, but little is known about its function. Analysis of Mfp-2 films using the surface forces apparatus detected no interaction between films or between a film and bare mica; however, addition of Ca(2+) and Fe(3+) induced significant reversible bridging (work of adhesion W(ad) approximately 0.3 mJ/m(2) to 2.2 mJ/m(2)) between two films at 0.35 m salinity. The strongest observed Fe(3+)-mediated bridging approaches the adhesion of oriented avidin-biotin complexes. Raman microscopy of plaque sections supports the co-localization of Mfp-2 and iron, which interact by forming bis- or tris-DOPA-iron complexes. Mfp-2 adhered strongly to Mfp-5, a DOPA-rich interfacial adhesive protein, but not to another interfacial protein, Mfp-3, which may in fact displace Mfp-2 from mica. In the presence of metal ions or Mfp-5, Mfp-2 adhesion was fully reversible. These results suggest that plaque cohesiveness depends on Mfp-2 complexation of metal ions, particularly Fe(3+) and also by Mfp-2 interaction with Mfp-5 at the plaque-substratum interface.
Hwang
Dong Soo
DS
Materials Research Laboratory, University of California, Santa Barbara, California 93106, USA.
Zeng
Hongbo
H
Masic
Admir
A
Harrington
Matthew J
MJ
Israelachvili
Jacob N
JN
Waite
J Herbert
JH
D000595:Amino Acid Sequence; D000818:Animals; D049872:Bivalvia; D002118:Calcium / Q000378:metabolism*; D022001:Focal Adhesions / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013059:Spectrum Analysis, Raman
D011506:Proteins; C037403:adhesive protein, mussel; D007501:Iron; D002118:Calcium