THE MAJOR BIOTINYL PROTEIN FROM PISUM-SATIVUM SEEDS COVALENTLY BINDS BIOTIN AT A NOVEL SITE

Seeds of Pisum sativum contain a biotinyl polypeptide called SBP65 tha t behaves as a putative sink for the free vitamin, representing more t han 90% of the total protein-bound biotin in mature seeds. A cDNA enco ding SBP65 was cloned and sequenced. The deduced primary structure of the protein was confirmed by protein sequencing. Peptide sequencing al so indicated binding of the biotin to lysine 103. The biotinylation do main of SBP65 differs markedly from that of presently known biotin enz ymes. Molecular analysis of the protein sequence reveals an extremely hydrophilic protein containing several repeated motifs. These properti es, as well as the temporal and spatial patterns of expression of this protein, suggest that SBP65 belongs to the LEA (late embryogenesis-ab undant) group of proteins.