Affinity purification of the photoreceptor cGMP-gated cation channel.
The cGMP-gated cation channel is a member of a new family of channel proteins that appear to be directly regulated by cyclic nucleotides. A protein with a subunit molecular mass of 78 kDa that exhibits cGMP-gated calcium flux when reconstituted into phospholipid-containing vesicles has been purified using 8-bromo-cGMP-agarose affinity chromatography. This channel activity is sensitive to the inhibitor l-cis-diltiazem. Treatment of the reconstituted channel with trypsin abolishes the l-cis-diltiazem sensitivity. Apparent endogenous proteolysis can also result in smaller molecular weight polypeptides that exhibit cGMP-gated channel activity but are insensitive to l-cis-diltiazem. These results show that the channel can bind cGMP and that it contains a l-cis-diltiazem inhibitory domain that is distinct from the cGMP-binding domain.
Hurwitz
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Department of Pediatrics and Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
Holcombe
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D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002846:Chromatography, Affinity; D006152:Cyclic GMP / Q000031:analogs & derivatives; D054815:Cyclic Nucleotide-Gated Cation Channels; D004110:Diltiazem / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000302:isolation & purification*; D007473:Ion Channels; D010786:Photoreceptor Cells / Q000737:chemistry*; D014357:Trypsin / Q000378:metabolism
D054815:Cyclic Nucleotide-Gated Cation Channels; D005136:Eye Proteins; D007473:Ion Channels; C016276:8-bromocyclic GMP; D014357:Trypsin; D004110:Diltiazem; D006152:Cyclic GMP