Partial characterization of dinoflagellate chromosomal proteins

Abstract

Dinoflagellate chromosomal proteins were analyzed by acrylamide gel electrophoresis. The electrophoretic pattern of acid-insoluble chromosomal proteins from Gyrodinium cohnii in sodium dodecylsulfate gels is less heterogeneous than that of corn, and is characterized by a paucity of bands representing molecular weights below 43 000. Acrylamide gel electrophoresis of G. cohnii and Peridinium trochoideum acid-soluble chromosomal proteins in urea at pH 3.2 gives a banding pattern quite different than that of typical histones. Acid-soluble protein from chromatin prepared by the two different methods and from both organisms migrates as one predominant band with a mobility slightly less than that of Histone IV from corn. Its molecular weight, estimated by sodium dodecylsulfate gel electrophoresis, is about 16000. It is a basic protein (basic/acidic amino acids 1.3) but differs from most histones in that it contains both cysteine and aromatic amino acids and somewhat lower levels of basic amino acids (18 mole % compared with 22 to 30% for histones). In addition, the major acid-soluble component is present in chromatin from log-phase cells but absent in chromatin from stationary-phase cells. For these reasons, the major acid-soluble protein is probably not a histone.