Polyadenylation site heterogeneity in mRNA encoding the precursor of the barley toxin β‐hordothionin

Abstract

Two cDNA clones, pTH2 and pTH3, encoding the precursor of the barley toxin β‐hordothionin have been identified and their nucleotide sequences determined. These sequences are identical, except that pTH2 is 22 bp longer than pTH3 at the 5'‐end and that the cleavage/poly(A) site of the mRNA represented by pTH3 is 4 positions further downstream from the single 5'‐AAUAAA‐3' polyadenylation signal than that of the pTH2 mRNA. In contrast, the cleavage/poly(A) site of the α‐hordothionin mRNA is 30 positions downstream from a second polyadenylation signal. The deduced amino acid sequence of the β‐hordothionin precursor differs from that of α‐hordothionin at 13 out of 127 positions.