The identification of additional subunits of the cGMP-gated cation cha
nnel suggests exciting questions about their regulatory roles and abou
t structure/functional relationships. How do the different subunits in
teract? How is the complex assembled into the plasma membrane? Divalen
t cations have been implicated in the regulation of adaptation. One of
ten overlooked cation is magnesium. Could this ion play a role in phot
otransduction?