Identification of a 27-kDa enkephalin-containing protein associated with bovine adrenal medullary chromaffin granule membranes by immunoblotting.

An antiserum which recognizes high molecular mass enkephalin-containing proteins was used to compare proenkephalin intermediates in both the soluble and membrane components of bovine adrenal chromaffin granules by immunoblotting. While a range of molecular mass forms were identified in the soluble lysate the major form in the membranes corresponded to a 27-kDa enkephalin-containing protein. Enzymic digestion of bands of 27-kDa material and quantitation of the enkephalin released showed that 22% of this material was membrane-associated. High concentrations of chaotropic agents were required to extract this material from the membranes. Association of hormone and neuropeptide precursors with membrane components may be important for targeting of precursors to secretory granules or correct processing.