The basic proteins of cell nuclei

Abstract

Cell nuclei have been isolated from various types of tissues. Evidence is presented which indicates that no appreciable loss of their major components occurs during isolation. Nuclei from normal cells of a particular type possess a constant composition characteristic of that type. The basic proteins extracted from such nuclei are not homogeneous. When they are of the histone type they can be separated into two parts conveniently described as a main histone and a subsidiary histone fraction respectively. A subsidiary product has also been obtained from protamins. A study of the chemical composition of the main histones and the protamins has shown that some of these are unquestionably species-specific. The phenomenon of cell specificity of these basic proteins has also been established in a number of instances. One case of cell specificity has also been found among the subsidiary histones. The difficulty of purification has prevented the detailed examination of others. The possible physiological significance of cell specificity of the basic proteins of cell nuclei is discussed.