Stereochemical course of the reaction catalyzed by guanylate cyclase from bovine retinal rod outer segments.

Koch, K W; Eckstein, Fritz; Stryer, Lubert

doi:10.1016/s0021-9258(19)38720-4

Cited by 71 publications

(10 citation statements)

References 25 publications

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“…The kinetics of guanylate cyclase and the features of its possible regulation by Ca are unknown in cones. We assumed that the enzyme in cones is functionally the same as that in rods (Koch and Stryer, 1988;Koch, Eckstein, and Stryer, 1990). Based on the experimental findings in rods we assumed the velocity of guanylate cyclase (VGc) to consist of a basal, Ca-independent activity of 4 I~M/s (V~c) and a Ca-dependent activity (VGc([Ca]i).…”

Section: Ca-dependent Regulation Of Guanylate Cyclasementioning

confidence: 99%

“…where VGm~ ~ is the enzyme's maximum velocity, which has a value of 95 ~M/s (Koch and Stryer, 1988;Koch et al, 1990). Km is the Michaelis constant of the enzyme for GTP.…”

Section: Ca-dependent Regulation Of Guanylate Cyclasementioning

confidence: 99%

“…Km is the Michaelis constant of the enzyme for GTP. The value of Km was taken to be 1 raM, as reported for the enzyme in rods (Krishnan, Fleischer, Chader, and Krishna, 1978;Fleischman and Denisevich, 1979;Koch et al, 1990). Guanylate cyclase activity depends only on cytoplasmic Ca concentration because the concentration of GTP can be expected to remain constant at 1 mM since this is the concentration of the nucleotide in the solution that fills the tight-seal electrode, which acts as an infinite source of GTP.…”

Section: Ca-dependent Regulation Of Guanylate Cyclasementioning

confidence: 99%

“…The decrease in cytoplasmic Ca activates guanylate cyclase. We assumed that the cyclase activity in cones is quantitatively the same as that measured in rods (Fleischman and Denisevich, 1979;Pepe et al, 1986;Koch and Stryer, 1988;Koch et al, 1990). The success of the model indicates that this assumption may be correct and that the cyclase in rods and cones may function with indistinguishable characteristics.…”

Section: Miller and Korenbrot Ca Control Of Cgmp Metabolic Cycle M Cone Photoreceptorsmentioning

confidence: 99%

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In retinal cones, membrane depolarization in darkness activates the cGMP-dependent conductance. A model of Ca homeostasis and the regulation of guanylate cyclase.

Miller

Korenbrot

1993

The Journal of General Physiology

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A B S T R A C T We measured outer segment currents under voltage clamp in solitary, single cone photoreceptors isolated from the retina of striped bass. In darkness, changes in membrane voltage to values more positive than 10 mV activate a timeand voltage-dependent outward current in the outer segment. This dark, voltageactivated current (DVAC) increases in amplitude with a sigmoidal time course up to a steady-state value, reached in 0.75-1.5 s. DVAC is entirely suppressed by light, and its current-voltage characteristics and reversal potential are the same as those of the light-sensitive currents. DVAC, therefore, arises from the activation by voltage in the dark of the light-sensitive, cGMP-gated channels of the cone outer segment. Since these channels are not directly gated by voltage, we explain DVAC as arising from a voltage-dependent decrease in cytoplasmic Ca concentration that, in turn, activates only guanylate cyclase and results in net synthesis of cGMP. This explanation is supported by the finding that the Ca buffer BAPTA, loaded into the cytoplasm of the cone outer segment, blocks DVAC. To link a decrease in cytoplasmic Ca concentration to the synthesis of cGMP and the characteristics of DVAC, we develop a quantitative model that assumes cytoplasmic Ca concentration can be continuously calculated from the balance between passive Ca influx via the cGMP-gated channel and its active efflux via a Na/Ca,K exchanger, and that further assumes that guanylate cyclase is activated by decreasing cytoplasmic Ca concentration with characteristics identical to those described for the enzyme in rods. The model successfully simulates experimental data by adjusting the Ca conductance of the cGMP-gated channels as a function of voltage and the Ca buffering power of the cytoplasm. This success suggests that the activity of guanylate cyclase in cone outer segments is indistinguishable from that in rods.

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Section: Ca-dependent Regulation Of Guanylate Cyclasementioning

confidence: 99%

“…where VGm~ ~ is the enzyme's maximum velocity, which has a value of 95 ~M/s (Koch and Stryer, 1988;Koch et al, 1990). Km is the Michaelis constant of the enzyme for GTP.…”

Section: Ca-dependent Regulation Of Guanylate Cyclasementioning

confidence: 99%

Section: Ca-dependent Regulation Of Guanylate Cyclasementioning

confidence: 99%

Section: Miller and Korenbrot Ca Control Of Cgmp Metabolic Cycle M Cone Photoreceptorsmentioning

confidence: 99%

See 2 more Smart Citations

In retinal cones, membrane depolarization in darkness activates the cGMP-dependent conductance. A model of Ca homeostasis and the regulation of guanylate cyclase.

Miller

Korenbrot

1993

The Journal of General Physiology

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“…The importance of this residue is borne out not only by its high conservation among all cyclases, but more recently by the finding that alanine substitution made at the analogous aspartic acid in the Ci subunit of soluble guanylyl cyclase serves as a (29). Elsewhere, it has been demonstrated that catalysis by guanylyl and adenylyl cyclases proceed through the same stereochemical course (30), thus it will be interesting to see if mutation of the analogous residue in adenylyl cyclase confers the same inhibition.…”

Section: Dominant N Egati Ve Mutations Of Guanylylmentioning

confidence: 99%

Dominant Negative Mutations of the Guanylyl Cyclase-A Receptor

Thompson

Garbers

1995

Journal of Biological Chemistry

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Guanylyl cyclase-A (GC-A), a receptor for A-type natriuretic peptide (ANP), contains an extracellular ligand-binding domain, a single transmembrane domain, and intracellular protein kinase-like and cyclase catalytic domains. Expression of the putative cyclase catalytic region (HCAT) resulted in the formation of an active enzyme that migrated as a homodimer on gel filtration columns; treatment with sodium trichloroacetate caused dissociation of the dimer and a loss of cyclase activity. Co-transfection of HCAT and full-length GC-A led to elevated basal intact cell cGMP concentrations and increased cell homogenate guanylyl cyclase activity. However, atrial natriuretic peptide-induced elevations of cGMP and cyclase activity were inhibited by the introduction of HCAT. Alanine scanning mutagenesis of highly conserved residues within HCAT identified one mutation (D893A) that destroyed enzyme activity but not the ability of the mutant subunit to form homodimers. The mutant subunit inhibited the cyclase activity of wild-type HCAT (approximately 70%) as well as that of full-length GC-A (approximately 85%) in co-expression studies where the amount of wild-type HCAT or full-length GC-A was not altered. Unlike co-transfection with wild-type HCAT, co-transfection of HCA-TD893A and GC-A did not result in elevated basal intact cell cGMP concentrations. For the first time we describe deletion and point mutations within the plasma membrane family of guanylyl cyclase receptors that result in the formation of effective dominant negative proteins.

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Functional consequences of single amino acid substitutions in calmodulin-activated adenylate cyclase of Bordetella pertussis.

et al. 1991

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Calmodulin‐activated adenylate cyclase of Bordetella pertussis and Bacillus anthracis are two cognate bacterial toxins. Three short regions of 13–24 amino acid residues in these proteins exhibit between 66 and 80% identity. Site‐directed mutagenesis of four residues in B. pertussis adenylate cyclase situated in the second (Asp188, Asp190) and third (His298, Glu301) segments of identity were accompanied by important decrease, or total loss, of enzyme activity. The calmodulin‐binding properties of mutated proteins showed no important differences when compared to the wild‐type enzyme. Apart from the loss of enzymatic activity, the most important change accompanying replacement of Asp188 by other amino acids was a dramatic decrease in binding of 3′‐anthraniloyl‐2′‐deoxyadenosine 5′‐triphosphate, a fluorescent analogue of ATP. From these results we concluded that the two neighbouring aspartic acid residues in B. pertussis adenylate cyclase, conserved in many other ATP‐utilizing enzymes, are essential for binding the Mg(2+)‐nucleotide complex, and for subsequent catalysis. Replacement of His298 and Glu301 by other amino acid residues affected the nucleotide‐binding properties of adenylate cyclase to a lesser degree suggesting that they might be important in the mechanism of enzyme activation by calmodulin, rather than being involved directly in catalysis.

show abstract

Stereochemical course of the reaction catalyzed by guanylate cyclase from bovine retinal rod outer segments.

Cited by 71 publications

References 25 publications

In retinal cones, membrane depolarization in darkness activates the cGMP-dependent conductance. A model of Ca homeostasis and the regulation of guanylate cyclase.

In retinal cones, membrane depolarization in darkness activates the cGMP-dependent conductance. A model of Ca homeostasis and the regulation of guanylate cyclase.

Dominant Negative Mutations of the Guanylyl Cyclase-A Receptor

Functional consequences of single amino acid substitutions in calmodulin-activated adenylate cyclase of Bordetella pertussis.

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