Figure 3.

Evidence that Ca-recoverin prolonged the flash response by slowing rhodopsin deactivation. Saturating flash responses in the presence of GTP (bold traces) without recoverin and with Ca-recoverin. During the response shown by the thin trace, GTP was transiently removed (timing shown above) with Ca-recoverin present throughout. Removal of GTP caused the flash response to deactivate, and reintroduction of GTP resulted in reactivation. Thirty micromolar Ca was present throughout. Concentration of myristoylated recoverin was 20 μM. Flash strength was 97 photons/μm². Time constants, τ, were (s): 5.8, control; 56, recoverin with GTP; 5.2, during GTP removal in recoverin (exponentials not shown). Absolute amplitudes (pA): 82, control; 55, recoverin with GTP; 59, recoverin with GTP removal. Junction currents induced by GTP removal have been subtracted.