Purification and characterization of perlucin and perlustrin, two new proteins from the shell of the mollusc Haliotis laevigata

Two new proteins, named perlucin and perlustrin, with M(r) 17,000 and 13,000, respectively, were isolated from the shell of the mollusc Halotis laevigata (abalone) by ion-exchange chromatography and reversed-phase HPLC after demineralization of the shell in 10% acetic acid. The sequence of the first 32 amino acids of perlucin indicated that this protein belonged to a heterogeneous group of proteins consisting of a single C-type lectin domain. Perlucin increased the precipitation of CaCO(3) from a saturated solution, indicating that it may promote the nucleation and/or the growth of CaCO(3) crystals. With pancreatic stone protein (lithostathine) and the eggshell protein ovocleidin 17, this is the third C-type lectin domain protein isolated from CaCO(3) biominerals. This indicates that this type of protein performs an important but at present unrecognized function in biomineralization. Perlustrin was a minor component of the protein mixture and the sequence of the first 33 amino acids indicated a certain similarity to part of the much larger nacre protein lustrin A.