Isolation and sequence of a gene encoding a methionine-rich 10-kDa zein protein from maize.

We have isolated the gene encoding a methionine-rich 10-kDa zein protein from a lambda EMBL3 maize genomic 'mini' library of the inbred line BSSS-53 and determined its nucleotide sequence. The sequence matches perfectly with a cDNA clone from the inbred line W22 (which has the same restriction fragment length polymorphism as many inbred lines tested) indicating that we have isolated a functional storage protein gene that is very conserved in maize. This comparison also excludes any splicing of any precursor mRNA and therefore any presence of introns. A number of potential regulatory sequences have been located in the flanking regions. The 10-kDa-zein gene represents the last size class in the zein multigene family to be characterized. Its structure allows us now to re-examine the relationship of all the zein proteins and also to compare the structure of a new class of storage proteins that are rich in methionine, an essential amino acid in livestock fodder.