M. Pauwels et al., INDUCTION BY ZINC OF SPECIFIC METALLOTHIONEIN ISOFORMS IN HUMAN MONOCYTES, European journal of biochemistry, 220(1), 1994, pp. 105-110
A low-molecular-mass zinc-containing protein was isolated by gel perme
ation and anion-exchange chromatography of lysates of human monocytes
induced with zinc acetate. Characterization by sodium dodecyl sulphate
/polyacrylamide gel electrophoresis and amino acid sequencing identifi
ed the two major charge-separable fractions and an occasionally occurr
ing third fraction as metallothionein-1, metallothionein-2 and metallo
thionein-0, respectively. Metallothionein-1 was shown to consist of a
mixture of isoforms, confirmed as metallothionein-1e, metallothionein-
1g and metallothionein-11 by comparison with cDNA sequences obtained b
y screening a human monocyte cDNA library. We can find no previous obs
ervation in the literature of metallothionein-1g at both the protein a
nd RNA level in a non-tumour cell, and of metallothionein-0 in a non-f
etal cell or tissue. Since isoform-specific polymerase-chain-reaction
amplification showed the presence of metallothionein-0 mRNA in zinc-in
duced but not in untreated monocytes, these cells can be used as an in
vitro system to investigate the expression of this previously conside
red fetal isoform.