Site of attachment of mercuribenzoate in crystals of an actin:DNase I complex.

Crystals of a complex of chicken gizzard G-actin and DNase I were soaked in a solution of radioactive 4-hydroxymercuribenzoate (MB). The soaked crystals, which contained 0.93 mol of MB per mol of G-actin, were dissolved in "G-buffer" and digested with trypsin, and the resulting peptides were fractionated by thin-layer chromatography. The MB is exchangeable between peptides that contain cysteine residues, but the data obtained here suggested that MB attached to the cysteine residue at the 373rd position of the G-actin molecule.