Epidermal growth factor binding proteins in rice (Oryza sativa L.) leaves

A ligand blotting experiment using [125I]epidermal growth factor (EGF) showed that there are EGF binding proteins in rice leaves. EGF binding proteins have isoelectric points and relative molecular masses of 5.5/35 kDa, 7.5/50 kDa and 8.3/40 kDa, respectively. The amino acid sequences of the N-terminal and internal regions of the EGF binding proteins were determined. The amino acid sequences of 35 kDa protein and 40 kDa were found to be homologous with those of the photosystem II oxygen-evolving complex. The amino acid sequence of the 50 kDa protein was homologous with that of riburose bisphosphate carboxylase/oxygenase. The presence of proteins capable of binding to EGF suggests the possibility of EGF-like regulation in plants.