39.

A GTP analog binds irreversibly to transducin. Gel filtration chromatography was performed before adding the GTP analog (panel A) and after binding the GTP analog (panel B). Only the second peak in panel B contained bound GTP analog.

A. Transduction without GTP analog B. Transduction afer binding GTP analog

These data probably result from the GTP analog

• a. breaking a disulfide bond between beta and gamma subunits.
• b. displacing GDP in the alpha-subunit, causing alpha subunit dissociation.
• c. dissociating a transducin dimer.
• d. inducing cleavage in a peptide bond in the alpha subunit.
• e. phosphorylating a serine in the beta subunit.