Purification and characterization of a dopa-containing protein from the foot of the Asian freshwater mussel, Limnoperna fortunei

A Dopa-containing protein was purified from the foot of the Asian freshwater mussel, Limnoperna fortunei, through acid-urea extraction, 36% ammonium sulfate precipitation, Sephacryl S-200 gel filtration, and reversed phase high performance liquid chromatography. The apparent molecular mass of the protein was 96 kDa, and Achromobacter protease I digested this into six major fragments. The amino acid sequences of the fragments were determined as two hexapeptides and four decapeptides. The consensus sequence of the decapeptides was Lys-(Hyp/Pro)-Thr-(Gln/Tyr)-Dopa-(Ser/Thr)-(Asp/Thr)-Glu-Tyr-Lys. These results suggest that the Dopa-containing foot protein mostly consists of repetitive decapeptides and hexapeptides. The Dopa-containing 96 kDa protein is considered to be a byssal precursor in L. fortunei.