title: Purification and characterization of a cadmium-induced metallothionein from the shore crab Carcinus maenas (L.).
abstract: Two metallothionein variants were purified from the midgut gland of crabs (Carcinus maenas) exposed to a high cadmium concentration (2 p.p.m.). One of the variants was purified from crabs exposed to a low cadmium concentration (0.5 p.p.m.). The purification method involved acetone precipitation, gel filtration and reversed-phase h.p.l.c. The complete amino acid sequences of both variants have been elucidated by m.s. and automated sequence analysis on S-methylated proteins or fragments produced by cleavage of the S-methylated proteins with Staphylococcus aureus proteinase. The two variants from crabs exposed to the high cadmium concentration differed only by a single residue of methionine at the N-terminus. The single variant isolated from crabs exposed to the low cadmium concentration was the one without the N-terminal methionine, indicating that high cadmium concentrations either inhibit the processing enzymes and/or that the processing enzymes cannot keep pace with the increased metallothionein synthesis when cadmium availability is high. Cadmium-induced metallothionein from C. maenas shows a high degree of structural similarity to metallothioneins from the decapod crustaceans Scylla serrata and Homarus americanus.
authors.affiliation: Institute of Biology, University of Odense, Denmark.
authors.forename: K L
authors.initials: KL
authors.lastname: Pedersen
authors.forename: S N
authors.initials: SN
authors.lastname: Pedersen
authors.forename: P
authors.initials: P
authors.lastname: Højrup
authors.forename: J S
authors.initials: JS
authors.lastname: Andersen
authors.forename: P
authors.initials: P
authors.lastname: Roepstorff
authors.forename: J
authors.initials: J
authors.lastname: Knudsen
authors.forename: M H
authors.initials: MH
authors.lastname: Depledge
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003386:Brachyura / Q000378:metabolism*; D002104:Cadmium / Q000494:pharmacology*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008668:Metallothionein / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification*; D008969:Molecular Sequence Data
chemical_list: D002104:Cadmium; D008668:Metallothionein