Characterization of embryo globulins encoded by the maize Glb genes

Two of the most abundant proteins in maize embryos are saline-soluble, water-insoluble globulins. One is a Mr 63,000 protein encoded by the Glb1 gene and the other is a Mr 45,000 component encoded by the Glb2 gene. Both proteins accumulate to high levels during embryo development and are rapidly degraded during the early stages of seed germination. Amino acid composition analysis indicates that these proteins may serve as storage reserves to provide sources of nitrogen and carbon to the germinating embryo. Amino-terminal sequence analysis of the final Glb1 gene product, GLB1, and its immediate precursor, GLB1', indicates that the latter is proteolytically cleaved near the amino terminus to form GLB1. In addition to these biochemical studies, we describe the identification of a novel maize variant which lacks the protein product of the Glb2 gene.