Type I Rhodopsins

Question

Type I rhodopsins:
A) are only found in prokaryotes.
B) are converted from 11-cis to all-trans retinal isomers by light.
C) can be used experimentally either to photo-activate or -inactivate mammalian neurons.
D) are closely related to type II rhodopsins in sequence and structure.
E) All of the above

Accepted Answer

Type I rhodopsins sense light in bacterial phototaxis, but they are also found in many eukaryotic microbes. They are quite different in sequence and structure from type II rhodopsins and are converted from all-trans retinal to 13-cis retinal by light. Channelrhodopsin 2 can mediate light-induced depolarization of mammalian neurons, while halorhodopsin (a chlorine pump) can be used to inactivate neurons.