Sequence interrelationships of the subunits of vicilin from pea seeds

Serological studies and comparison of N-terminal amino acid sequences with the amino acid sequence deduced from a cDNA clone have been used to establish the sequence relationships between the subunits of the pea seed storage protein, vicilin. Subunits smaller than Mr∼50 000 (i.e., Mr 34 000, 30 000, 25 000, 18 000, 14 000, 13 000 and 12 000) show extensive homology with molecules within Mr∼50 000 group. Both the sequencing and serological data confirm earlier evidence from studies on vicilin synthesisin vivo andin vitro which indicated that the vicilin subunits smaller than Mr∼50 000 arose by endoproteolytic cleavage of parent molecules within the Mr∼50 000 group. Cleavage in different Mr 50 000 parent molecules containing either one or both of two susceptible processing sites accounts for the formation of all the vicilin subunits smaller than Mr∼50 000, with the possible exception of the Mr34 000 polypeptide. The position of these sites in the putative parents were defined by reference to a complete amino acid sequence deduced from the sequence of DNA complementary to mRNA for one member of the Mr∼50 000 group.