Isolation and characterisation of zinc-binding proteins distinct from metallothionein from the eggs of the sea urchin Strongylocentrotus intermedius

Two low-molecular-weight zinc-binding proteins were purified from eggs of the sea urchin Strongylocentrotus intermedius (Echinodermata: Echinoidea) by gel-permeation and anion-exchange chromatography followed by high performance liquid chromatography. The characteristics of these proteins are distinct from those of metallothionein. Amino acid compositions show a low or intermediate content of cysteine and high amounts of acidic amino acids, glycine and histidine; they also contain methionine and aromatic residues. On the basis of these characteristics, the S. intermedius zinc-binding proteins appear similar to other metalloproteins isolated from both vertebrates and invertebrates. No typical metallothionein was detected in the extracts from S. intel medius eggs.