The effect of the γ-subunit of the cyclic GMP phosphodiesterase of bovine and frog (Rana catesbiana) retinal rod outer segments on the kinetic parameters of the enzyme

Rod-outer-segment cyclic GMP phosphodiesterase (PDE) (subunit composition alpha beta gamma 2) contains catalytic activity in alpha beta. The gamma-subunits are inhibitors. Removal of the gamma-subunits increases Vmax. without affecting the Km. The inhibitory effect of a single gamma-subunit (alpha beta gamma) on the Vmax. of alpha beta is much greater in bovine than in frog (Rana catesbiana) PDE. Bovine PDE in the alpha beta gamma 2 state has a Vmax. that is 2.6 +/- 0.4% of the Vmax. of alpha beta. The removal of one gamma-subunit to give alpha beta gamma results in a Vmax. 5.2 +/- 1% of that for maximal activity. Frog alpha beta gamma 2 has a Vmax. 10.8 +/- 2%, and alpha beta gamma has a Vmax. 50 +/- 18%, of the Vmax. of alpha beta. These data suggest that a single gamma-subunit can inhibit the catalytic activity of active sites on both alpha- and beta-subunits in bovine, but not in frog, rod-outer-segment PDE.

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Effect of monoclonal antibody binding on .alpha.-.beta..gamma. subunit interactions in the rod outer segment G protein, Gt

Biochemistry ◽

10.1021/bi00451a047 ◽

1989 ◽

Vol 28 (25) ◽

pp. 9873-9880 ◽

Cited By ~ 19

Author(s):

Maria R. Mazzoni ◽

Heidi E. Hamm

Keyword(s):

Monoclonal Antibody ◽

G Protein ◽

Outer Segment ◽

Antibody Binding ◽

Subunit Interactions ◽

Gamma Subunit ◽

Rod Outer Segment ◽

Alpha Beta ◽

Monoclonal Antibody Binding

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Comparison of the phosphodiesterase inhibitory subunit interactions of frog and bovine rod outer segments

Biochemical Journal ◽

10.1042/bj2590013 ◽

1989 ◽

Vol 259 (1) ◽

pp. 13-19 ◽

Cited By ~ 42

Author(s):

M M Whalen ◽

M W Bitensky

Keyword(s):

Catalytic Activity ◽

Binding Sites ◽

Outer Segment ◽

Rod Outer Segments ◽

Rod Outer Segment ◽

Outer Segments ◽

Frog Retina ◽

Inhibitory Site ◽

Alpha Beta ◽

Gamma S

The rod outer segments of the bovine and frog retina possess a cyclic GMP phosphodiesterase (PDE) that is composed of two larger subunits, alpha and beta (P alpha beta), which contain the catalytic activity and a smaller gamma (P gamma) subunit which inhibits the catalytic activity. We studied the binding of P gamma to P alpha beta in both the bovine and frog rod outer segment membranes. Analysis of these data indicates that there are two classes of P gamma binding sites per P alpha beta in both species. The activation of PDE by the guanosine 5′-[gamma-thio]triphosphate form of the alpha subunit of transducin, T alpha.GTP gamma S, was also studied. These data indicate that the two classes of P gamma binding sites contribute to the formation of two classes of binding sites for T alpha.GTP gamma S. We demonstrate solubilization of a portion of the P gamma by T alpha.GTP gamma S in both species. There is also present, in both species, a second class of P gamma which is not solubilized even when it is dissociated from its inhibitory site on P alpha beta by T alpha.GTP gamma S. The amount of full PDE activity which results from release of the solubilizable P gamma is about 50% in the frog PDE but only approx. 17% in the bovine PDE. We also show that activation of frog rod outer segment PDE by trypsin treatment releases the PDE from the membranes. This type of release by trypsin has already been demonstrated in bovine rod outer segments [Wensel & Stryer (1986) Proteins: Struct. Funct. Genet. 1, 90-99].

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Activation mechanism of rod outer segment cyclic GMP phosphodiesterase. Release of inhibitor by the GTP/GTP-binding protein.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(20)82047-x ◽

1983 ◽

Vol 258 (13) ◽

pp. 8188-8194

Author(s):

A Yamazaki ◽

P J Stein ◽

N Chernoff ◽

M W Bitensky

Keyword(s):

Cyclic Gmp ◽

Outer Segment ◽

Binding Protein ◽

Activation Mechanism ◽

Gtp Binding Protein ◽

Rod Outer Segment ◽

Gtp Binding

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On a soluble system for studying light activation of rod outer segment cyclic GMP phosphodiesterase

Neurochemical Research ◽

10.1007/bf00966017 ◽

1977 ◽

Vol 2 (1) ◽

pp. 1-10 ◽

Cited By ~ 37

Author(s):

A. Sitaramayya ◽

N. Virmaux ◽

P. Mandel

Keyword(s):

Cyclic Gmp ◽

Outer Segment ◽

Light Activation ◽

Rod Outer Segment

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Structural and functional characterization of the rod outer segment membrane guanylate cyclase

Biochemical Journal ◽

10.1042/bj3020455 ◽

1994 ◽

Vol 302 (2) ◽

pp. 455-461 ◽

Cited By ~ 90

Author(s):

R M Goraczniak ◽

T Duda ◽

A Sitaramayya ◽

R K Sharma

Keyword(s):

Cyclic Gmp ◽

Outer Segment ◽

Photoreceptor Cell ◽

Functional Characterization ◽

Visual Signal ◽

Membrane Guanylate Cyclase ◽

Rod Outer Segment ◽

Vertebrate Photoreceptor ◽

Hydrolysis Of

In the vertebrate photoreceptor cell, rod outer segment (ROS) is the site of visual signal-transduction process, and a pivotal molecule that regulates this process is cyclic GMP. Cyclic GMP controls the cationic conductance into the ROS, and light causes a decrease in the conductance by activating hydrolysis of the cyclic nucleotide. The identity of the granylate cyclase (ROS-GC) that synthesizes this pool of cyclic GMP is unknown. We now report the cloning, expression and functional characterization of a DNA from bovine retina that encodes ROS-GC.

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