Open AccessPurification and primary structure of snail metallothionein
Author(s) -
DALLINGER Reinhard,
BERGER Burkhard,
HUNZIKER Peter E.,
BIRCHLER Neil,
HAUER Charles R.,
KÄAGI Jeremias H. R.
Publication year - 1993
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1993.tb18193.x
Subject(s) - metallothionein , edman degradation , helix pomatia , snail , biochemistry , amino acid , cysteine , protein primary structure , chemistry , biology , peptide sequence , peptide , enzyme , ecology , gene
A cadmium‐binding metallothionein has been purified from metal‐exposed Roman snails ( Helix pomatia ) using gel‐permeation, ion‐exchange and reverse‐phase high‐performance liquid chromatorgraphy. The S ‐methylated protein was digested with trypsin and the endoproteinases Asp‐N, Glu‐C and Arg‐C. While most of the resulting peptides could be sequenced by Edman degradation, the intact protein, as well as the N‐terminal peptide, proved to be blocked. Analysis by mass spectrometry showed that the N‐terminal amino acid was an acetylated serine residue. Snail metallothionein, which is suggested to be involved in the detoxification of cadmium, contains 66 amino acid residues, 18 of which are cysteine residues arranged in seven Cys‐Xaa‐Cys motifs. The calculated molecular mass of the protein is 6.62 kDa. The primary structure of snail metallothionein reveals a clear relationship with molluscan and vertebrate metallothioneins, but lower similarity with metallothioneins of other invertebrate species. The N‐terminal region of the isolated protein proved to be unique among the metallothionein sequences determined so far, showing high degrees of similarity with the N‐terminal sequences of histones H2A and H4 which may be important for regulatory functions.