Crab metallothionein. Primary structures of metallothioneins 1 and 2.

The complete amino acid sequences of metallothioneins 1 and 2 from the crab Scylla serrata are reported. The primary structures were determined by automated and manual sequence analysis on fragments produced by cleavage of the S-pyridylethylated, S-aminoethylated, and S-carbamidomethylated proteins with trypsin. The two isoproteins consist of 58 and 57 amino acid residues, respectively, and show a sequence identity of 83%. Comparison of their primary structures with the known sequences of three representative mammalian metallothioneins and Neurospora copper metallothionein reveals a high degree of sequence homology among the six proteins. The abundant cysteinyl residues were found to be strongly conserved, in agreement with their function as metal ligands (see following paper by Otvos, J. D., Olafson, R. W., and Armitage, I. M. (1982). J. Biol. Chem. 257, 2427-2431.