Variation in the primary structure of waxy proteins (granule-bound starch synthase) in diploid cereals

The molecular weights of waxy proteins, by SDS-PAGE, and the N-terminal amino acid sequences of mature protein and of V8 protease-induced fragments were determined in diploid cereals. The homology of the primary structure was relatively high among cereals examined here, and there appeared to be a common sequence, V-F-V-G-A-E-M-A, in the vicinity of the N terminus. Based on the amino acid sequences, these cereals could be divided into two groups, including corn and rice in one and diploid wheat, four Aegilops species, rye, and barley in the other. In diploid wheat and Aegilops species there were substitutions of amino acids in the primary structure. Variations of this sort suggest that the primary structure of waxy proteins would provide clues to the phylogenetic relations in the wheat group.