Structural characterization of the isoforms of neonatal and adult rat liver metallothionein

Metallothionein was purified from the livers of adult and neonatal rats. The complete amino acid sequences of isoforms I and II of Cd-induced adult metallothionein were determined by automated Edman degradation of CNBr and tryptic peptides of carboxymethylated proteins. Both isoproteins contain 61 r...

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Bibliographic Details
Published in:The Journal of biological chemistry 1984-09, Vol.259 (18), p.11419-11425
Main Authors: Winge, D R, Nielson, K B, Zeikus, R D, Gray, W R
Format: Article
Language:English
Subjects:
Age Factors
Amino Acid Sequence
Analytical, structural and metabolic biochemistry
Animals
Biological and medical sciences
Chromatography, High Pressure Liquid
Chromatography, Ion Exchange
Cyanogen Bromide
Electrophoresis, Polyacrylamide Gel
Fundamental and applied biological sciences. Psychology
Gene Expression Regulation
Liver - analysis
Male
Metalloproteins
Metallothionein - analysis
Metallothionein - genetics
Other metalloproteins
Proteins
Rats
Rats, Inbred Strains
Trypsin - metabolism
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Summary:Metallothionein was purified from the livers of adult and neonatal rats. The complete amino acid sequences of isoforms I and II of Cd-induced adult metallothionein were determined by automated Edman degradation of CNBr and tryptic peptides of carboxymethylated proteins. Both isoproteins contain 61 residues, but differ at 12 of those positions. The positions of the 20 cysteinyl residues are invariant with respect to those in other known mammalian metallothioneins. Based on the following criteria, the two soluble and constitutive Zn-metallothionein isoforms from neonatal liver appear identical to their corresponding forms in the adult animal: 1) they behave identically on reverse-phase high-pressure liquid chromatography, anion-exchange chromatography and nondenaturing gel electrophoresis; 2) their amino acid compositions are the same within experimental error; and 3) their amino acid sequences are identical in the first 23 residues, even though isoforms I and II differ in 7 of those positions. It appears highly likely that isoforms from both neonatal and adult rats are encoded by the same genes, and therefore that the large age-dependent concentration differences seen in the liver must be due to variation in gene regulation.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(18)90877-X