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D'Amours MR, Cote RH. Regulation of photoreceptor phosphodiesterase catalysis by its non-catalytic cGMP-binding sites. Biochem J 1999; 340 ( Pt 3):863-9. [PMID: 10359674 PMCID: PMC1220321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The photoreceptor 3':5'-cyclic nucleotide phosphodiesterase (PDE) is the central enzyme of visual excitation in rod photoreceptors. The hydrolytic activity of PDE is precisely regulated by its inhibitory gamma subunit (Pgamma), which binds directly to the catalytic site. We examined the inhibition of frog rod outer segment PDE by endogenous Pgamma, as well as by synthetic peptides corresponding to its central and C-terminal domains, to determine whether the non-catalytic cGMP-binding sites on the catalytic alphabeta dimer of PDE allosterically regulate PDE activity. We found that the apparent binding affinity of Pgamma for PDE was 28 pM when cGMP occupied the non-catalytic sites, whereas Pgamma had an apparent affinity only 1/16 of this when the sites were empty. The elevated basal activity of PDE with empty non-catalytic sites can be decreased by the addition of nanomolar levels of cGMP, demonstrating that the high-affinity non-catalytic sites on the PDE catalytic dimer mediate this effect. No evidence for a direct allosteric effect of the non-catalytic sites on catalysis could be detected for the activated enzyme lacking bound Pgamma. The intrinsic affinity of a synthetic C-terminal (residues 63-87) Pgamma peptide to bind and to inhibit the hydrolytic activity of activated PDE was enhanced 300-fold in the presence of cGMP compared with cAMP. We conclude that the binding of cGMP to the non-catalytic sites of PDE induces an allosteric change in the structure of the catalytic domain that greatly enhances the interaction of the C-terminus of Pgamma with the catalytic domain.
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Affiliation(s)
- M R D'Amours
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, NH 03824-3544, USA
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2
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Peter Hofmann K, Heck M. Light-induced protein-protein interactions on the rod photoreceptor disc membrane. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1874-5342(07)80006-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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3
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Udovichenko IP, Cunnick J, Gonzalez K, Takemoto DJ. The visual transduction and the phosphoinositide system: a link. Cell Signal 1994; 6:601-5. [PMID: 7857764 DOI: 10.1016/0898-6568(94)90043-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- I P Udovichenko
- Department of Biochemistry, Kansas State University, Manhattan 66506
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4
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Tsuboi S, Matsumoto H, Yamazaki A. Phosphorylation of an inhibitory subunit of cGMP phosphodiesterase in Rana catesbeiana rod photoreceptors. II. A possible mechanism for the turnoff of cGMP phosphodiesterase without GTP hydrolysis. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36568-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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5
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Cunnick J, Twamley C, Udovichenko I, Gonzalez K, Takemoto DJ. Identification of a binding site on retinal transducin alpha for the phosphodiesterase inhibitory gamma subunit. Biochem J 1994; 297 ( Pt 1):87-91. [PMID: 8280114 PMCID: PMC1137794 DOI: 10.1042/bj2970087] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Transducin alpha (T alpha) activates retinal rod cyclic GMP phosphodiesterase (PDE) by interacting with and removing the inhibitory PDE gamma subunit. A T alpha-PDE gamma complex can be isolated in vitro, and our previous work [Morrison, Rider and Takemoto (1987) FEBS Lett. 222, 266-270; Morrison, Cunnick, Oppert and Takemoto (1989) J. Biol. Chem. 264, 11671-11681] has identified a region of PDE gamma, residues 24-45, that binds to T alpha. The C-terminal region of PDE gamma is the site that interacts with PDE alpha/beta and inhibits catalytic function. The site on T alpha that binds to the PDE gamma 24-45 region has not been identified. Synthetic peptides (15-mers) which span the bovine T alpha sequence were tested for binding to purified recombinant PDE gamma using a solid-phase assay. The peptides were also tested for ability to activate a PDE complex. We have identified a region, residues 250-275 of T alpha, which shows a high affinity of PDE gamma and for the PDE gamma (24-45) binding peptide. The peptide did not bind to the C-terminal residues 50-87 of PDE gamma. Likewise, a region of T alpha, 1-25 did not exhibit high-affinity binding to PDE gamma or to the 24-45 PDE gamma peptide. Specific binding of the 250-275 peptide to PDE gamma was confirmed by its ability to compete with T alpha binding to PDE gamma, although a higher concentration was required (10x). The T alpha-(250-275) peptide activated a fully inhibited PDE alpha beta gamma 2 complex in a dose-dependent manner. These results suggest that a region on T alpha that recognizes the PDE gamma-binding site is found within residues 250-275 of T alpha.
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Affiliation(s)
- J Cunnick
- Department of Biochemistry, Kansas State University, Manhattan 66506
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6
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Takemoto DJ, Gonzalez K, Udovichenko I, Cunnick J. Cyclic GMP-regulated cyclic nucleotide phosphodiesterases. Cell Signal 1993; 5:549-53. [PMID: 8312132 DOI: 10.1016/0898-6568(93)90050-v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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7
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Heck M, Hofmann KP. G-protein-effector coupling: a real-time light-scattering assay for transducin-phosphodiesterase interaction. Biochemistry 1993; 32:8220-7. [PMID: 8394130 DOI: 10.1021/bi00083a024] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We describe a real-time assay for the interaction of the G-protein of retinal rods, transducin (Gt), with its effector, cGMP phosphodiesterase (PDE). The purified proteins were recombined with isolated rod disk membranes. Reactions were triggered by flash photolysis of the receptor rhodopsin, and monitored by changes of near-infrared light scattering (LS signals). PDE-related LS signals from membrane preparations have been described by others [Caretta, A., & Stein, P. J. (1986) Biochemistry 25, 2335-2341; Bennett, N., & Clerc, A. (1992) Biochemistry 31, 1858-1866]. In the present study, the previous overall light-scattering (turbidity) approach was improved by a specific optical setup and millisecond time resolution. This allowed isolation of a fast "PDE signal" which monitors Gt-PDE interaction on the membrane and in real time. The assignment to the reaction is made by the following observations: (i) preactivation of PDE by purified G alpha GTP gamma S gradually suppresses the signal; (ii) the peak amplitude of the signal is stoichiometric with respect to both Gt and PDE; and (iii) the rise and delay time fit into a kinetic model for a reaction of activated Gt (G*). A comparative investigation, relating the PDE signal with Gt activation and PDE enzymatic activity, led to the following results: (i) the apparent dissociation constant for the interaction of G* with the first binding site on membrane-bound PDE is less than 2.5 nM; (ii) the time interval between formation of G* and its interaction with PDE is less than 5 ms; (iii) membrane-bound PDE, even in its preactivated form, slows the release of G* from the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Heck
- Institut für Biophysik und Strahlenbiologie, Freiburg, FRG
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8
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Lipkin VM, Bondarenko VA, Zagranichny VE, Dobrynina LN, Muradov KG. Site-directed mutagenesis of the cGMP phosphodiesterase gamma subunit from bovine rod outer segments: role of separate amino acid residues in the interaction with catalytic subunits and transducin alpha subunit. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1176:250-6. [PMID: 8385997 DOI: 10.1016/0167-4889(93)90052-q] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The recombinant and 21 mutant phosphodiesterase (PDE) gamma subunit (PDE gamma) genes were expressed by sequential transcription and translation in vitro. Inhibitory properties of these mutants and their interactions with PDE catalytic and transducin alpha subunits were studied. The interaction of the PDE gamma subunit with the catalytic ones proceeds in two steps--primary binding and inhibition. The central region of the PDE gamma molecule enriched with the basic amino acid residues (particularly, Lys-29, Lys-31 and Arg-33), is involved in the primary binding, and the PDE gamma C-terminus plays the key role in inhibition. The spatial orientation of the C-terminus is of great importance here. The PDE gamma C-terminus also affects binding to catalytic moieties.
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Affiliation(s)
- V M Lipkin
- Branch of Shemyakin Institute of Bioorganic Chemistry, Russian Academy of Sciences, Pushchino, Moscow Region
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9
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Arshavsky V, Dumke C, Bownds M. Noncatalytic cGMP-binding sites of amphibian rod cGMP phosphodiesterase control interaction with its inhibitory gamma-subunits. A putative regulatory mechanism of the rod photoresponse. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)35793-4] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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10
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Brown RL. Functional regions of the inhibitory subunit of retinal rod cGMP phosphodiesterase identified by site-specific mutagenesis and fluorescence spectroscopy. Biochemistry 1992; 31:5918-25. [PMID: 1319205 DOI: 10.1021/bi00140a031] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In the dark, the activity of the cGMP phosphodiesterase (PDE) of retinal rod outer segments is held in check by its two inhibitory gamma subunits. Following illumination, gamma is rapidly removed from its inhibitory site by transducin, the G-protein of the visual system. In order to probe the functional roles of specific regions in the PDE gamma primary sequence, 10 variants of PDE gamma have been produced by site-specific mutagenesis and expression in bacteria and their properties compared to those of protein containing the wild-type bovine PDE gamma amino acid sequence. Three questions were asked about each mutant: What is its affinity for the alpha beta catalytic subunit of PDE? Does it inhibit catalytic activity? If so, can transducin relieve this inhibition? Binding to PDE alpha beta was determined directly using fluorescein-labeled gamma by measuring the increase in emission anisotropy that occurs when gamma binds to alpha beta. Inhibition of PDE alpha beta was measured by reconstitution of the gamma variants with gamma-free PDE generated by limited digestion with trypsin or endoproteinase Arg-C. Unlike trypsin, the latter enzyme did not remove PDE's ability to bind membranes and be activated by transducin, so that transducin activation of PDE containing specific gamma variants could be assayed directly. The results indicate that mutations in many regions of gamma affect its binding to alpha beta. A mutant missing the last five carboxy-terminal residues (83-87) was totally lacking in inhibitory activity. However, it still bound to PDE alpha beta tightly, although with a 100-fold lower dissociation constant (approximately 5 nM) than that of wild-type gamma (approximately 50 pM).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R L Brown
- Department of Cell Biology, Stanford University, California 94305
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11
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Artemyev NO, Hamm HE. Two-site high-affinity interaction between inhibitory and catalytic subunits of rod cyclic GMP phosphodiesterase. Biochem J 1992; 283 ( Pt 1):273-9. [PMID: 1314566 PMCID: PMC1131025 DOI: 10.1042/bj2830273] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Light-activated cyclic GMP-phosphodiesterase (PDE) is the key effector enzyme of vertebrate photoreceptor cells which regulates the level of the internal transmitter cyclic GMP. PDE consists of catalytic P alpha and P beta subunits, and two copies of inhibitory P gamma subunit. The two P gamma subunits block the enzyme's activity in the dark and are removed by the alpha-subunit of transducin (alpha 1) upon light-activation of photoreceptor cells. Here we have examined the role of various regions of P gamma, the N-terminal, the central cationic and the C-terminal regions, in interaction with the catalytic subunits of PDE. N-Terminal truncation of P gamma (12-87-P gamma) did not change the potency of PDE inhibition, and thus we conclude that the P gamma N-terminal region is not critical for P gamma-P alpha beta interaction. The central region, 24-46-P gamma, participates in interaction with the catalytic P alpha beta subunits. A synthetic peptide corresponding to this site inhibited approximately 50% of trypsin-activated PDE (tPDE) (Ki approximately 15 microM) and competed with P gamma for inhibition of tPDE. We demonstrated, by using h.p.l.c. gel filtration, that 125I-Tyr-24-46-P gamma peptide bound with high affinity to tPDE, but not to P alpha beta gamma 2. The C-terminal region of 46-87-P gamma was found to be the major region involved in inhibition of PDE. It fully inhibited tPDE with a Ki of approximately 0.8 microM. It also bound to tPDE, but not P alpha beta gamma 2, in h.p.l.c. gel-filtration experiments. In addition, P gamma was cross-linked by p-phenylenedimaleimide to both P alpha and P beta, as was shown by using subunit-specific anti-P alpha, -P beta and -P gamma antibodies. Cys68 of P gamma, which presumably participates in cross-linking, is located near the P gamma C-terminus. These data provide evidence for two regions of P gamma that interact with, and inhibit, P alpha beta. The central region, 24-46 P gamma, is important in binding, but inhibits PDE only weakly, whereas the C-terminal region is most important for PDE inhibition. These results help to explain the well-known fact that P gamma trypsin-activation and C-terminal truncation both lead to PDE activation. Furthermore, our findings on the mechanism of PDE inhibition of P gamma are relevant for understanding the mechanism of PDE activation by transducin.
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Affiliation(s)
- N O Artemyev
- Department of Physiology and Biophysics, University of Illinois College of Medicine, Chicago 60680
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12
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Takemoto DJ, Hurt D, Oppert B, Cunnick J. Domain mapping of the retinal cyclic GMP phosphodiesterase gamma-subunit. Function of the domains encoded by the three exons of the gamma-subunit gene. Biochem J 1992; 281 ( Pt 3):637-43. [PMID: 1311170 PMCID: PMC1130737 DOI: 10.1042/bj2810637] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Retinal rod-outer-segment phosphodiesterase (PDE) is a heterotetramer consisting of two similar, but not identical, catalytic subunits (alpha and beta) and two identical inhibitory subunits (gamma 2). Previously, we have reported that the site of PDE alpha/beta interaction with PDE gamma is located within residues 54-87 [Cunnick, Hurt, Oppert, Sakamoto & Takemoto (1990) Biochem. J. 271, 721-727]. The site for PDE gamma interaction with transducin alpha (T alpha) was found to encompass residues 24-45 of PDE gamma [Morrison, Cunnick, Oppert & Takemoto (1989) J. Biol. Chem. 264, 11671-11681]. In order to identify binding sites and other functional domains of PDE gamma, the three peptides which are encoded by the three exons of the PDE gamma gene were synthesized chemically. These exons encode for residues 1-49, 50-62 and 63-87 of bovine PDE gamma [Piriev, Purishko, Khramtsov & Lipkin (1990) Dokl. Akad. Nauk. SSSR 315, 229-230]. The peptide encompassing residues 63-87 was inhibitory in a PDE assay, whereas peptides 1-49 and 50-62 had no effect. However, both peptides 1-49 and 63-87 bound to PDE alpha/beta in a solid-phase binding assay. Only peptide 1-49 bound to T alpha.GTP[S] (GTP[S] is guanosine 5'-[gamma-thio]triphosphate). These data confirm that the inhibitory region of PDE gamma is encoded by exon 3 (residues 63-87), whereas a separate binding site for PDE alpha/beta and for T alpha.GTP[S] is encoded by exon 1 (residues 1-49). To study further the structure-function relationship of PDE gamma, this entire protein and two mutants were chemically synthesized. One mutant (-CT) lacked residues 78-87, whereas another replaced tyrosine-84 with glycine (TYR-84). Whereas the synthetic PDE gamma inhibited PDE alpha/beta catalytic activity, the -CT and TVR-84 mutants did not. All three synthetic proteins bound to both PDE alpha/beta and and T alpha.GTP[S]. These data confirm the presence of an alternative binding site on PDE gamma and demonstrate the importance of tyrosine-84 in PDE gamma inhibitory activity.
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Affiliation(s)
- D J Takemoto
- Department of Biochemistry, Kansas State University, Manhattan 66506
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13
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Gonzalez K, Cunnick J, Takemoto D. Retinal cyclic-GMP phosphodiesterase gamma-subunit: identification of functional residues in the inhibitory region. Biochem Biophys Res Commun 1991; 181:1094-6. [PMID: 1662493 DOI: 10.1016/0006-291x(91)92050-t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Previously, we have domain-mapped the 87 amino acid PDE gamma inhibitory subunit of the retinal phosphodiesterase (PDE) alpha beta gamma 2 complex using synthetic peptides. The PDE gamma subunit has a binding domain for transducin-alpha (T alpha) and for PDE alpha/beta within residues # 24-45 and an inhibitory region for PDE alpha/beta within residues # 80-87. In order to establish the role of individual amino acids in the function of the PDE gamma inhibitory subunit, peptides of PDE gamma # 63-87 and mutant peptides were synthesized and utilized in PDE inhibition assays. The following peptides exhibited a decreased ability to inhibit PDE alpha/beta: All were from PDE gamma # 63-87; PDE gamma Tyr 84----Gly, PDE gamma Phe 73----Gly and PDE gamma Gln 83----Gly.
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Affiliation(s)
- K Gonzalez
- Department of Biochemistry, Kansas State University, Manhattan 66506
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14
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Oppert B, Gonzalez K, Hurt D, Cunnick J, Takemoto D. Retinal cyclic-GMP phosphodiesterase gamma-subunit: use of mutant synthetic peptides to define function. Biochem Biophys Res Commun 1991; 181:306-9. [PMID: 1659809 DOI: 10.1016/s0006-291x(05)81418-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Previously, we have domain-mapped the 87 amino acid PDE gamma inhibitory subunit of the retinal phosphodiesterase (PDE) alpha beta gamma 2 complex using synthetic peptides (1). The PDE gamma subunit has a binding domain for transducin-alpha (T alpha) and for PDE alpha/beta within residues #24-45. An inhibitory region for PDE alpha/beta is within residues #80-87. In order to establish the role of individual amino acids in the function of the PDE gamma inhibitory subunit, mutants were synthesized and utilized in PDE inhibition assays. The following mutants exhibited a decreased ability to inhibit PDE alpha/beta: Tyr84----Gly; Arg24----Gly; and Arg33----Pro. Sequence comparisons with cone PDE gamma indicate that there is identity within these functional regions.
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Affiliation(s)
- B Oppert
- Department of Biochemistry, Kansas State University, Manhattan 66506
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Oppert B, Cunnick J, Hurt D, Takemoto D. Identification of the retinal cyclic GMP phosphodiesterase inhibitory gamma-subunit interaction sites on the catalytic alpha-subunit. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55344-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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16
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Oppert B, Takemoto DJ. Identification of the gamma-subunit interaction sites in the retinal cyclic-GMP phosphodiesterase beta-subunit. Biochem Biophys Res Commun 1991; 178:474-9. [PMID: 1650192 DOI: 10.1016/0006-291x(91)90131-p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Using synthetic peptides, the identification of the retinal cyclic-GMP phosphodiesterase (cGMP PDE) interaction sites for the inhibitory gamma-subunit in the catalytic alpha-subunit were recently localized to residues #16-30 and 78-90 in the alpha-subunit (1). In this study, a binding radioimmunoassay (RIA) showed a weak interaction between PDE gamma and PDE beta subunits in PDE beta residues #15-34, and stronger interaction sites were found in residues #91-110 and 211-230. Sequence comparison between PDE alpha and PDE beta illustrate some differences in these regions, particularly in PDE alpha 16-30 and PDE beta 15-34 regions. Differences in interaction sites in PDE alpha and PDE beta for PDE gamma may account for the differences in affinities observed between PDE gamma and the catalytic subunits.
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Affiliation(s)
- B Oppert
- Department of Biochemistry, Kansas State University, Manhattan 66506
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