Chromosomal proteins in Saccharomyces cerevisiae : I. number and properties of individual proteins.

Proteins were isolated from purified yeast chromatin and subjected to two-dimensional electrophoresis. The cellular and the chromosomal content of the major nonhistone proteins was measured. Two polypeptides of molecular weights 55,000 and 53,000, identified as α and β tubulin, and a polypeptide of molecular weight 63,000, associated with the nuclear DNA to a very high degree, account for nearly 50% of the nonhistone proteins present in chromatin. Only one tenth of the RNA polymerase subunit with the molecular weight of 23,000 was associated with nuclear DNA following chromatin purification in metrizamide gradients.