A METHOD FOR PROBING THE TOPOGRAPHY AND INTERACTIONS OF PROTEINS - FOOTPRINTING OF MYOGLOBIN

We describe a procedure for mapping residues on the surface of a prote in molecule to its sequence, using a scheme that is analogous to nucle ic acid footprinting. The protein is end labeled radioactively and sub jected to limited proteolysis, and the products are analyzed by denatu ring polyacrylamide gel electrophoresis and autoradiography. The metho d is tested with the heme protein myoglobin and applied to mapping the (unknown) surface of the molecule lacking the heme group: apomyoglobi n. Sites of protein-protein interaction can be identified, as illustra ted by footprinting the association between myoglobin and an anti-myog lobin monoclonal antibody.