Purification and identification of photoreceptor guanylate cyclase.
Photoreceptor guanylate cyclase was solubilized and purified from bovine rod outer segments with 50-150-fold increase in specific activity using the nonionic detergent n-dodecyl-beta-D-maltoside. Guanylate cyclase activities correlated with the enrichment of a protein with an apparent Mr = 112,000. The purified enzyme showed specific activities of 100-700 nmol of cGMP produced/min/mg protein and exhibited positive cooperativity with respect to MnGTP (Hill coefficient n = 1.6 +/- 0.1). The apparent Km was 274 +/- 67 microM, and the turnover number was determined to be 0.2-1.3 cGMP produced/s. The molar ratio of the 112-kDa protein to rhodopsin corresponds to 1:104. This indicates that the amount of guanylate cyclase in rod photoreceptors is nearly equimolar to the amount of the phosphodiesterase.
Koch
K W
KW
Institut für Biologische Informationsverarbeitung, Forschungszentrum Jülich, Federal Republic of Germany.
D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006157:Guanosine Monophosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006162:Guanylate Cyclase / Q000302:isolation & purification* / Q000378:metabolism; D010786:Photoreceptor Cells / Q000201:enzymology*; D012995:Solubility
C037047:manganese GTP; D006157:Guanosine Monophosphate; D006160:Guanosine Triphosphate; D006162:Guanylate Cyclase