<unk> s are a group of transmembrane proteins that form ion channels; pores which open or close in response to<unk> . Most<unk> s have been synthesized in the laboratory for study, though one naturally occurring example, Channelrhodopsin, is currently known. There are, however, many known photoreceptor proteins, which act in a similar manner to<unk> s but are generally G protein coupled receptors and not actually gated ion channels.
Light-gated ion channel
Cyclic nucleotide-gated ion channel
Voltage-gated ion channel
Calcium channel
Chloride channel
Ion transporter
Voltage-dependent calcium channel
Magnesium transporters