Purification and partial amino acid sequence of a novel protein of the reticulocalbin family

Binding proteins in neuronal membranes for a phospholipase A2 with presynaptic neurotoxicity have been purified. Three polypeptides of 87, 65, and 50 K Da were obtained from the synaptic membrane fraction of guinea pig brain utilizing an immobilized crotoxin (a phospholipase A2) column. For large scale purification, porcine brain was used instead, and two polypeptides of 50 and 18 K Da were found. The 65 and 18 K polypeptides may represent hitherto unidentified components of the crotoxin-binding proteins. Partial N-terminal amino acid sequence and a partial sequence for an internal peptide fragment have been determined for the 50 K polypeptide. Search of protein data bank reveals that this polypeptide or protein is a novel member of the reticulocalbin family of calcium-binding proteins.