INTERACTION OF POLY(L-LYSINE) AND COPOLYMERS OF LYSINE WITH IMMOBILIZED DNA

Sonicated DNA has been covalently attached to Sepharose 4B by a carbodiimide method [Rickwood, P. (1972) Biochim. Biophys. Acta 269, 47-50] which minimizes modification of the DNA and matrix. Columns of this material have been used to study the interaction between cationic polypeptides and DNA. When poly(l-lysine) is bound to such columns at low ionic strength and then eluted with a linear salt gradient the polypeptide elutes over a broad range of salt concentration, presumably reflecting different strengths of interaction with various sites on the DNA. The broadness of the elution profile cannot be attributed to heterogeneity in the poly(l-lysine) sample but rather to the AT GC content of various DNA sites. Studies with other polypeptides, poly(l-Lys79, l-Leu21) and poly-(l-Lys-l-Ala-Gly), as well as studies at different temperatures, have helped to clarify the possible roles of conformational mobility, polypeptide hydrophobicity, and the presence of contiguous lysines in determining the strength of interaction of polypeptides and proteins with DNA sites. © 1979.