Total RNA from human reticulocytes mas purified and reverse-transcribe
d into cDNA using an oligo-dT primer, This cDNA was used as a template
for a polymerase chain reaction (PCR) with a primer specific for the
N-terminal sequence of mammalian metallothioneins (MT) and a universal
primer, A single amplified fragment was thus generated which when clo
ned and sequenced revealed two distinct MT cDNAs of almost identical m
olecular weights. One sequence was identical to that previously report
ed for human MT II and the other encoded a novel MT I isoform (MT I-R)
The DNA sequence of MT 1(R) is distinct from those documented for oth
er MT I isoforms.