Chromogranin-A (CgA) is a ubiquitous protein which colocalizes in secretory granules of multiple endocrine tissues and cosecretes with peptide hormones from these tissues. Although the function of CgA has remained unknown, there has been recent interest in its potential role as a prohormone for smaller, biologically active peptides. We isolated and characterized a 26-kDa N-terminal fragment of CgA which is a natural breakdown product of bovine parathyroid CgA in storage. A similar, if not identical, fragment of CgA is secreted by bovine parathyroid glands. The secreted fragment elutes on HPLC and migrates on both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and acid-urea gels in the same position as the 26-kDa N-terminal fragment. When added to the incubation medium of dispersed bovine parathyroid cells, the 26-kDa N-terminal fragment of CgA inhibits the low calcium-stimulated secretion of both PTH and CgA. This N-terminal fragment is homologous to betagranin, which is a 21-kDa N-terminal fragment of CgA that is generated from CgA in rat insulin granules. Thus, a naturally occurring betagranin-like N-terminal fragment of bovine parathyroid CgA is not only secreted itself, but can inhibit the secretion of PTH and intact CgA by bovine parathyroid cells. The processing of intact CgA to fragments such as the N-terminal fragment that we describe may be important in the autocrine or paracrine regulation of secretion.

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Candida albicans possesses on its cell surface an adhesin which binds the whole viable fungus to subendothelial extracellular matrix and matrix proteins. The adhesin is composed of 75 to 801%Y carbohydrate and approximately 20 to 25% protein by weight. High-performance liquid chromatography of material eluted from a fibronectin-agarose aifinity column demonstrates the presence of three peaks, all ofwhich on sodium dodecyl sulfate-polyacrylamide gel electrophoresis show the presence of one protein of approximately 60 kDa. Molecular weight sizing column chromatography, however, demonstrates that the adhesin elutes with an apparent molecular mass of 42 kDa. The N terminus of the 60-kDa glycoprotein is blocked to Edman degradation. The fibronectin adhesin of C. albicans is a glycoprotein that may be present and functional as an aggregate or multimer of a 60-kDa protein.