Vol. 127, No. 1, 1985 February 28, 1985 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 380-383 THE AMINO TERMINAL SEQUENCES OF BOVINE AND HUMAN CHROMOGRANIN A AND SECRETORY PROTEIN I ARE IDENTICAL William Kruggel 1, Daniel T. O'Connor 2, and Randolph V. Lewis 1'3 IDept. of Biochemistry, University of Wyoming, Laramie, WY 82071 2Dept. of Medicine, University of California, and Veterans Administration Medical Center, San Diego, CA 92161 Received January 25, 1985 The amino terminal sequences of bovine and human adrenal medullary chromogranln A have been determined. Their sequences are identical and also identical to the published sequence of secretory protein I from the parathyroid gland. This data indicates that the previously published sequence of chromogranin A is incorrect at residues 2 and 19. These data confirm earlier observations of a substantial similarity between secretory protein I and chromogranin A and, in fact, strongly suggest that they are identical. © 1985 Academic Press, Inc. Chromogranin A is a protein costored and coreleased with catecholamines from storage granules in the adrenal medulla (1,2), while secretory protein I (parathyroid secretory protein) is a protein costored and coreleesed with parathyroid hormone from storage granules in the parathyroid gland (3,4). A recent publication demonstrated a strong similarity between secretory protein I and chromogranin A (5). The data included similar amino acid composition, physical properties, and immunological cross reactivity. The amino terminal sequences were shown to differ in two positions, residues 2 and 19 (4,5,6). During the course of our studies on peptides in the adrenal medulla we isolated two peptides whose sequences corresponded exactly to the amino terminal sequences of secretory protein I but not to that of chromogranin A (7). To determine if these peptides did in fact originate from chromogranin A we have sequenced the amino terminal 25 residues of both human and bovine chromogranin A. Immunohistochemistry (8-11) and radiolmmunoassays (12,13) 3To whom correspondence should be addressed. 0006-291X/85 $1.50 Copyright © 1985 by Academic Press, Inc. All rights of reproduction in any form reserved. 380