Figure 1.

Procedure for mapping nucleosome core–HMG-14 interactions. Radioactively labeled S-[N-(4-azidosalicyl)cysteaminyl]-2-thiopyridyl is attached to either 7C or 88C HMG-14 point mutants. The labeled point mutants are complexed with nucleosome cores and the phenylazide moiety is activated by exposure to UV. The bond between the HMG protein and the crosslinking agent is disrupted by 2-mercaptoethanol, and the target of crosslinking is identified by polyacrylamide gel electrophoresis and autoradiography. The ¹²⁵I-labeled histones are purified by HPLC and proteolyzed, and the resulting peptides are fractionated by HPLC and polyacrylamide gel electrophoresis. The targeted peptides are detected by autoradiography and identified by their amino acid sequence. See text for further details.