Chapter 18. Chromatin-Bound Proteases and Their Inhibitors

Abstract

This chapter describes chromatin-bound proteases and their inhibitors. Chromatin-bound neutral protease is extractable in acid with the lysine-rich histones. Chromatography of the acid extract on a sephadex G-100 column has been found to exhibit a neutral protease of 24,000 daltons. Purification of the neutral protease is achieved by salt extraction of calf thymus chromatin and subsequent gel filtration on sephadex G-75. The purified protease shows a preference for nucleohistone as a substrate when compared to hemoglobin or bovine serum albumin. The methods discussed in this chapter are directed toward an understanding of how a particular chromatin preparation can be routinely assayed for proteolytic activity and block proteolytic activity in a variety of denaturing solvents. Moreover, work in the laboratory is currently being directed to fractionation and isolation of the three diisopropylfluorophosphate (DFP)-binding proteins in rat liver nuclei. Whether the two high-molecular weight DFP-binding proteins of rat liver nuclei are proteases or are perhaps precursors of proteases is being investigated. This information may aid in the assignment of a biological role for the protease activity endogenous to chromatin.