Sea Urchin Metallothionein Sequence: Key to an Evolutionary Diversity

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 82; no. 15; pp. 4992 - 4994
• Main Authors: Nemer, Martin, Wilkinson, David G., Travaglini, Elizabeth C., Sternberg, Edmund J., Butt, Tauseef R.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.08.1985; National Acad Sciences
• Subjects: Amino Acid Sequence; Amino acids; Analytical, structural and metabolic biochemistry; Animals; Binding Sites; Biological and medical sciences; Biological Evolution; Brachyura - genetics; Crabs; Drosophila; Fundamental and applied biological sciences. Psychology; Heavy metals; Mammals - genetics; Messenger RNA; Metalloproteins; Metallothionein - genetics; Molecules; Neurospora; Neurospora - genetics; Nucleotide sequences; Other metalloproteins; Proteins; Sea urchins; Sea Urchins - genetics; Yeasts; Yeast; Molecular structure; Echinodermata; Drosophila; Biological evolution; Primary structure; Metalloproteins; Fungi; Vertebrata; Mammalia; Animal; Invertebrata; Metallothionein; Thallophyta
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.82.15.4992

The metallothioneins (MTs) constitute a diverse family of proteins, which are enriched in cysteines and bind heavy metals. The amino acid sequence of sea urchin MT has been obtained from its mRNA sequence and compared with MT sequences of various sources. A largely conserved sequence of 10 amino acids, the ``central segment,'' is located near the center of the MT molecules of Neurospora, yeast, and Drosophila and the center of putative domains in mammalian and sea urchin MTs. The sea urchin carboxyl-terminal-half MT resembles the mammalian 9-cysteine amino-terminal MT domain I, both in the presence of this central segment and in the relative placement of cysteine residues. Conversely, the sea urchin amino-terminal-half MT, containing 11 cysteines, resembles the mammalian carboxyl-terminal MT domain II in its exclusive enrichment in vicinal cysteines. The reversed order of these sea urchin and mammalian MT halves appears to be just one aspect of a diversity based on the elaboration of structures containing the central segment. Still another variation in this diversity is the duplication of the central segment, apparent in Drosophila and crab MTs.