The primary structure of bovine chromogranin A: a representative of a class of acidic secretory proteins common to a variety of peptidergic cells

We have determined the primary structure of bovine chromogranin A as a first step in the elucidation of the function of this widespread protein. After oligonucleotide screening of a cDNA library of bovine adrenal medulla, a clone (insert length 1.9 kb) containing the entire coding region for chromogranin A was isolated and sequenced. The authenticity of the sequence was verified by comparison with N‐terminal, several internal, and C‐terminal amino acid sequences as well as the amino acid composition of chromogranin A. The cDNA clone hybridized to an mRNA of 2.1 kb and, after in vitro transcription‐translation, yielded a polypeptide with a similar electrophoretic mobility in SDS gels to chromogranin A. The polypeptide chain of chromogranin A comprises 431 amino acid residues, corresponding to an unmodified protein of 48 kd, and is preceded by a cleaved signal peptide of 18 amino acid residues. Interesting features of the chromogranin A structure include repeated clusters of glutamic acid residues, the occurrence of eight potential dibasic cleavage sites, six of which are located in the C‐terminal domain, and the presence, in the N‐terminal domain, of ‐Arg‐Gly‐Asp‐ (RGD), a three amino acid sequence involved in the binding of several constitutively secreted proteins to cell membranes.