The deduced amino acid sequences of the
-polypeptides of
Pisum legumin from two loci on chromosome 1 were compared with one from a locus on chromosome 7. The chromosome 1-derived sequences were
80% identical, but each was only
50% homologous to the chromosome 7-derived sequence. Comparison of these sequences with those of homologous polypeptides from two other species of the Leguminoseae showed that the chromosome 1-derived
Pisum sequences were more similar to legumin B than to legumin A from
Vicia faba and were more closely related to group II than to group I glycinins from
Glycine max. The converse was true for the chromosome 7-derived
Pisum sequences. This suggests that divergence of legumin-like sequences predated speciation in these three members of the Leguminosease.
Among the three
Pisum sequence classes, a highly variable region was identified within the
-polypeptide, just to the amino-terminal side of the
processing site. This region varied considerably in length within the three classes of
Pisum -polypeptide sequence, a variation which far exceeded that which has previously been described for other legumins and glycinins. The chromosome 7-derived, and one of the chromosome 1-derived
-polypeptide sequences contained different tandem repeats in this region.