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Svensson B, Nitu FR, Rebbeck RT, McGurran LM, Oda T, Thomas DD, Bers DM, Cornea RL. Molecular Mechanism of a FRET Biosensor for the Cardiac Ryanodine Receptor Pathologically Leaky State. Int J Mol Sci 2023; 24:12547. [PMID: 37628726 PMCID: PMC10454150 DOI: 10.3390/ijms241612547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 07/31/2023] [Accepted: 08/02/2023] [Indexed: 08/27/2023] Open
Abstract
Ca2+ leak from cardiomyocyte sarcoplasmic reticulum (SR) via hyperactive resting cardiac ryanodine receptor channels (RyR2) is pro-arrhythmic. An exogenous peptide (DPc10) binding promotes leaky RyR2 in cardiomyocytes and reports on that endogenous state. Conversely, calmodulin (CaM) binding inhibits RyR2 leak and low CaM affinity is diagnostic of leaky RyR2. These observations have led to designing a FRET biosensor for drug discovery targeting RyR2. We used FRET to clarify the molecular mechanism driving the DPc10-CaM interdependence when binding RyR2 in SR vesicles. We used donor-FKBP12.6 (D-FKBP) to resolve RyR2 binding of acceptor-CaM (A-CaM). In low nanomolar Ca2+, DPc10 decreased both FRETmax (under saturating [A-CaM]) and the CaM/RyR2 binding affinity. In micromolar Ca2+, DPc10 decreased FRETmax without affecting CaM/RyR2 binding affinity. This correlates with the analysis of fluorescence-lifetime-detected FRET, indicating that DPc10 lowers occupancy of the RyR2 CaM-binding sites in nanomolar (not micromolar) Ca2+ and lengthens D-FKBP/A-CaM distances independent of [Ca2+]. To observe DPc10/RyR2 binding, we used acceptor-DPc10 (A-DPc10). CaM weakens A-DPc10/RyR2 binding, with this effect being larger in micromolar versus nanomolar Ca2+. Moreover, A-DPc10/RyR2 binding is cooperative in a CaM- and FKBP-dependent manner, suggesting that both endogenous modulators promote concerted structural changes between RyR2 protomers for channel regulation. Aided by the analysis of cryo-EM structures, these insights inform further development of the DPc10-CaM paradigm for therapeutic discovery targeting RyR2.
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Affiliation(s)
- Bengt Svensson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Florentin R. Nitu
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Robyn T. Rebbeck
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Lindsey M. McGurran
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Tetsuro Oda
- Department of Pharmacology, University of California, Davis, CA 95616, USA
| | - David D. Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis, CA 95616, USA
| | - Razvan L. Cornea
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
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Svensson B, Nitu FR, Rebbeck RT, McGurran LM, Oda T, Thomas DD, Bers DM, Cornea RL. Molecular Mechanism of a FRET Biosensor for the Cardiac Ryanodine Receptor Pathologically Leaky State. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.07.548138. [PMID: 37461514 PMCID: PMC10350043 DOI: 10.1101/2023.07.07.548138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
Ca 2+ leak from cardiomyocyte sarcoplasmic reticulum (SR) via hyperactive resting cardiac ryanodine receptor channels (RyR2) is pro-arrhythmic. An exogenous peptide, (DPc10) detects leaky RyR2 in cardiomyocytes. Conversely, calmodulin (CaM) inhibits RyR2 leak. These observations have led to designing a FRET biosensor for drug discovery targeting RyR2. Here we used FRET to understand the molecular mechanism driving the DPc10-CaM interdependence when binding RyR2 in SR vesicles. We used donor-FKBP12.6 (D-FKBP) to resolve RyR2 binding of acceptor-CaM (A-CaM). In low nanomolar Ca 2+ , DPc10 decreased both FRET max (under saturating [A-CaM]) and the CaM/RyR2 binding affinity. In micromolar Ca 2+ , DPc10 decreased FRET max without affecting CaM/RyR2 binding affinity. This correlates with analysis of fluorescence-lifetime-detected FRET indicating that DPc10 lowers occupancy of the RyR2 CaM-binding sites in nanomolar (not micromolar) Ca 2+ and lengthens D-FKBP/A-CaM distances independent of [Ca 2+ ]. To observe DPc10/RyR2 binding, we used acceptor-DPc10 (A-DPc10). CaM weakens A-DPc10/RyR2 binding, this effect being larger in micromolar vs. nanomolar Ca 2+ . Moreover, A-DPc10/RyR2 binding is cooperative in CaM- and FKBP-dependent manner, suggesting that both endogenous modulators promote concerted structural changes between RyR2 protomers for channel regulation. Aided by analysis of cryo-EM structures, these insights inform further development of the DPc10-CaM paradigm for therapeutic discovery targeting RyR2.
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Affiliation(s)
- Bengt Svensson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Florentin R. Nitu
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Robyn T. Rebbeck
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Lindsey M. McGurran
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Tetsuro Oda
- Department of Pharmacology, University of California, Davis
| | - David D. Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis
| | - Razvan L. Cornea
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
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Walweel K, Oo YW, Laver DR. The emerging role of calmodulin regulation of RyR2 in controlling heart rhythm, the progression of heart failure and the antiarrhythmic action of dantrolene. Clin Exp Pharmacol Physiol 2017; 44:135-142. [PMID: 27626620 DOI: 10.1111/1440-1681.12669] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 08/27/2016] [Accepted: 09/09/2016] [Indexed: 11/28/2022]
Abstract
Cardiac output and rhythm depend on the release and the take-up of calcium from the sarcoplasmic reticulum (SR). Excessive diastolic calcium leak from the SR due to dysfunctional calcium release channels (RyR2) contributes to the formation of delayed after-depolarizations, which underlie the fatal arrhythmias that occur in heart failure and inherited syndromes. Calmodulin (CaM) is a calcium-binding protein that regulates target proteins and acts as a calcium sensor. CaM is comprised of two calcium-binding EF-hand domains and a flexible linker. CaM is an accessory protein that partially inhibits RyR2 channel activity. CaM is critical for normal cardiac function, and altered CaM binding and efficacy may contribute to defects in SR calcium release. The present paper reviews CaM binding to RyR2 and how it regulates RyR2 channel activity. It then goes on to review how mutations in the CaM amino acid sequence give rise to inherited syndromes such as Catecholaminergic Polymorphic Ventricular Tachychardia (CPVT) and long QT syndrome (LQTS). In addition, the role of reduced CaM binding to RyR2 that results from RyR2 phosphorylation or from oxidation of either RyR2 or CaM contributes to the progression of heart failure is reviewed. Finally, this manuscript reviews recent evidence that CaM binding to RyR2 is required for the inhibitory action of a pharmaceutical agent (dantrolene) on RyR2. Dantrolene is a clinically used muscle relaxant that has recently been found to exert antiarrhythmic effects against SR Ca2+ overload arrhythmias.
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Affiliation(s)
- Kafa Walweel
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW, 2308, Australia
| | - Ye Win Oo
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW, 2308, Australia
| | - Derek R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW, 2308, Australia
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Faltinova A, Tomaskova N, Antalik M, Sevcik J, Zahradnikova A. The N-Terminal Region of the Ryanodine Receptor Affects Channel Activation. Front Physiol 2017; 8:443. [PMID: 28713282 PMCID: PMC5492033 DOI: 10.3389/fphys.2017.00443] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 06/12/2017] [Indexed: 11/29/2022] Open
Abstract
Mutations in the cardiac ryanodine receptor (RyR2), the ion channel responsible for release of calcium ions from intracellular stores into cytoplasm, are the cause of several inherited cardiac arrhythmias. At the molecular level, disease symptoms can be mimicked by domain peptides from mutation-prone regions of RyR2 that bind to RyR2 and activate it. Here we show that the domain peptide DPcpvtN2, corresponding to the central helix of the N-terminal region of RyR2, activates the RyR2 channel. Structural modeling of interaction between DPcpvtN2 and the N-terminal region of RyR2 in the closed and open conformation provided three plausible structures of the complex. Only one of them could explain the dependence of RyR2 activity on concentration of DPcpvtN2. The structure of the complex was at odds with the previously proposed “domain switch” mechanism of competition between domain peptides and ryanodine receptor domains. Likewise, in structural models of the N-terminal region, the conformational changes induced by DPcpvtN2 binding were different from those induced by mutation of central helix amino acids. The activating effect of DPcpvtN2 binding and of mutations in the central helix could be explained by their similar effect on the transition energy between the closed and open conformation of RyR2.
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Affiliation(s)
- Andrea Faltinova
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics of the Centre of Biosciences, Slovak Academy of SciencesBratislava, Slovakia.,Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of SciencesBratislava, Slovakia
| | - Nataša Tomaskova
- Faculty of Science, Institute of Chemical Sciences, Pavol Jozef Šafárik UniversityKošice, Slovakia
| | - Marián Antalik
- Faculty of Science, Institute of Chemical Sciences, Pavol Jozef Šafárik UniversityKošice, Slovakia
| | - Jozef Sevcik
- Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of SciencesBratislava, Slovakia
| | - Alexandra Zahradnikova
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics of the Centre of Biosciences, Slovak Academy of SciencesBratislava, Slovakia.,Department of Biochemistry and Structural Biology, Institute of Molecular Biology, Slovak Academy of SciencesBratislava, Slovakia
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Tatulian SA. Molecular-scale GPS: positioning a biosensor peptide on RyR. Biophys J 2015; 107:2003-5. [PMID: 25418085 DOI: 10.1016/j.bpj.2014.09.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 09/06/2014] [Accepted: 09/19/2014] [Indexed: 10/24/2022] Open
Affiliation(s)
- Suren A Tatulian
- Department of Physics, University of Central Florida, Orlando, Florida.
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Abstract
AbstractThe effect of a domain peptide DPCPVTc from the central region of the RYR2 on ryanodine receptors from rat heart has been examined in planar lipid bilayers. At a zero holding potential and at 8 mmol L−1 luminal Ca2+ concentration, DPCPVTc induced concentrationdependent activation of the ryanodine receptor that led up to 20-fold increase of PO at saturating DPCPVTc concentrations. DPCPVTc prolonged RyR2 openings and increased RyR2 opening frequency. At all peptide concentrations the channels displayed large variability in open probability, open time and frequency of openings. With increasing peptide concentration, the fraction of high open probability records increased together with their open time. The closed times of neither low- nor high-open probability records depended on peptide concentration. The concentration dependence of all gating parameters had EC50 of 20 μmol L−1 and a Hill slope of 2. Comparison of the effects of DPCPVTc with the effects of ATP and cytosolic Ca2+ suggests that activation does not involve luminal feed-through and is not caused by modulation of the cytosolic activation A-site. The data suggest that although “domain unzipping” by DPCPVTc occurs in both modes of RyR activity, it affects RyR gating only when the channel resides in the H-mode of activity.
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Tencerová B, Zahradníková A, Gaburjáková J, Gaburjáková M. Luminal Ca2+ controls activation of the cardiac ryanodine receptor by ATP. ACTA ACUST UNITED AC 2012; 140:93-108. [PMID: 22851674 PMCID: PMC3409101 DOI: 10.1085/jgp.201110708] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The synergic effect of luminal Ca2+, cytosolic Ca2+, and cytosolic adenosine triphosphate (ATP) on activation of cardiac ryanodine receptor (RYR2) channels was examined in planar lipid bilayers. The dose–response of RYR2 gating activity to ATP was characterized at a diastolic cytosolic Ca2+ concentration of 100 nM over a range of luminal Ca2+ concentrations and, vice versa, at a diastolic luminal Ca2+ concentration of 1 mM over a range of cytosolic Ca2+ concentrations. Low level of luminal Ca2+ (1 mM) significantly increased the affinity of the RYR2 channel for ATP but without substantial activation of the channel. Higher levels of luminal Ca2+ (8–53 mM) markedly amplified the effects of ATP on the RYR2 activity by selectively increasing the maximal RYR2 activation by ATP, without affecting the affinity of the channel to ATP. Near-diastolic cytosolic Ca2+ levels (<500 nM) greatly amplified the effects of luminal Ca2+. Fractional inhibition by cytosolic Mg2+ was not affected by luminal Ca2+. In models, the effects of luminal and cytosolic Ca2+ could be explained by modulation of the allosteric effect of ATP on the RYR2 channel. Our results suggest that luminal Ca2+ ions potentiate the RYR2 gating activity in the presence of ATP predominantly by binding to a luminal site with an apparent affinity in the millimolar range, over which local luminal Ca2+ likely varies in cardiac myocytes.
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Affiliation(s)
- Barbora Tencerová
- Institute of Molecular Physiology and Genetics, Centre of Excellence for Cardiovascular Research, Slovak Academy of Sciences, 833 34 Bratislava, Slovak Republic
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Meli AC, Refaat MM, Dura M, Reiken S, Wronska A, Wojciak J, Carroll J, Scheinman MM, Marks AR. A novel ryanodine receptor mutation linked to sudden death increases sensitivity to cytosolic calcium. Circ Res 2011; 109:281-90. [PMID: 21659649 DOI: 10.1161/circresaha.111.244970] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Mutations in the cardiac type 2 ryanodine receptor (RyR2) have been linked to catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT-associated RyR2 mutations cause fatal ventricular arrhythmias in young individuals during β-adrenergic stimulation. OBJECTIVE This study sought to determine the effects of a novel RyR2-G230C mutation and whether this mutation and RyR2-P2328S alter the sensitivity of the channel to luminal calcium (Ca(2+)). METHODS AND RESULTS Functional characterizations of recombinant human RyR2-G230C channels were performed under conditions mimicking stress. Human RyR2 mutant channels were generated by site-directed mutagenesis and heterologously expressed in HEK293 cells together with calstabin2. RyR2 channels were measured to examine the regulation of the channels by cytosolic versus luminal sarcoplasmic reticulum Ca(2+). A 50-year-old white man with repeated syncopal episodes after exercise had a cardiac arrest and harbored the mutation RyR2-G230C. cAMP-dependent protein kinase-phosphorylated RyR2-G230C channels exhibited a significantly higher open probability at diastolic Ca(2+) concentrations, associated with a depletion of calstabin2. The luminal Ca(2+) sensitivities of RyR2-G230C and RyR2-P2328S channels were WT-like. CONCLUSIONS The RyR2-G230C mutant exhibits similar biophysical defects compared with previously characterized CPVT mutations: decreased binding of the stabilizing subunit calstabin2 and a leftward shift in the Ca(2+) dependence for activation under conditions that simulate exercise, consistent with a "leaky" channel. Both RyR2-G230C and RyR2-P2328S channels exhibit normal luminal Ca(2+) activation. Thus, diastolic sarcoplasmic reticulum Ca(2+) leak caused by reduced calstabin2 binding and a leftward shift in the Ca(2+) dependence for activation by diastolic levels of cytosolic Ca(2+) is a common mechanism underlying CPVT.
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Affiliation(s)
- Albano C Meli
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, College of Physicians and Surgeons of Columbia University, New York, NY, USA
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Thomas NL, Maxwell C, Mukherjee S, Williams AJ. Ryanodine receptor mutations in arrhythmia: The continuing mystery of channel dysfunction. FEBS Lett 2010; 584:2153-60. [PMID: 20132818 DOI: 10.1016/j.febslet.2010.01.057] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 01/27/2010] [Accepted: 01/29/2010] [Indexed: 11/13/2022]
Abstract
Mutations in RyR2 are causative of an inherited disorder which often results in sudden cardiac death. Dysfunctional channel behaviour has been the subject of many investigations varying from single channel analysis through to complex animal models. This review discusses recent advances in the field, describes the controversy surrounding the exact consequences of RyR2 mutation and how the disparate data may be reconciled. This heterogeneity of function with respect to the effects of polymorphisms, phosphorylation, cytosolic and luminal Ca(2+) as well as inter-domain interactions may have important implications for the recent pharmaceutical therapies which have been put forward. We surmise that a comprehensive characterisation of mutations on a case-by-case basis may be beneficial for the development of specifically targeted therapies.
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Affiliation(s)
- N Lowri Thomas
- Department of Cardiology, Wales Heart Research Institute, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.
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Laver DR. Luminal Ca(2+) activation of cardiac ryanodine receptors by luminal and cytoplasmic domains. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:19-26. [PMID: 19255753 DOI: 10.1007/s00249-009-0417-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 01/28/2009] [Accepted: 02/02/2009] [Indexed: 10/21/2022]
Abstract
The ryanodine receptors form the calcium release channel in the membrane of the sarcoplasmic reticulum (SR, the main intracellular Ca(2+) store). The importance of ryanodine receptors (RyRs) to cardiac pacemaking and rhythmicity is highlighted by more than 69 mutations, RyR mutations, which underlie arrhythmias and sudden cardiac death. Although most of these mutations lie in cytoplasmic domains, they all cause increased RyR activation by Ca(2+) in the SR lumen. Presented here is a review of the mechanisms by which cytoplasmic domains of the RyR can determine luminal activation.
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Affiliation(s)
- Derek R Laver
- School of Biomedical Sciences, Hunter Medical Research Institute, University of Newcastle, Callaghan, NSW, 2308, Australia.
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Laver DR, Honen BN. Luminal Mg2+, a key factor controlling RYR2-mediated Ca2+ release: cytoplasmic and luminal regulation modeled in a tetrameric channel. ACTA ACUST UNITED AC 2008; 132:429-46. [PMID: 18824590 PMCID: PMC2553390 DOI: 10.1085/jgp.200810001] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In cardiac muscle, intracellular Ca(2+) and Mg(2+) are potent regulators of calcium release from the sarcoplasmic reticulum (SR). It is well known that the free [Ca(2+)] in the SR ([Ca(2+)](L)) stimulates the Ca(2+) release channels (ryanodine receptor [RYR]2). However, little is known about the action of luminal Mg(2+), which has not been regarded as an important regulator of Ca(2+) release. The effects of luminal Ca(2+) and Mg(2+) on sheep RYR2 were measured in lipid bilayers. Cytoplasmic and luminal Ca(2+) produced a synergistic increase in the opening rate of RYRs. A novel, high affinity inhibition of RYR2 by luminal Mg(2+) was observed, pointing to an important physiological role for luminal Mg(2+) in cardiac muscle. At diastolic [Ca(2+)](C), luminal Mg(2+) inhibition was voltage independent, with K(i) = 45 microM at luminal [Ca(2+)] ([Ca(2+)](L)) = 100 microM. Luminal and cytoplasmic Mg(2+) inhibition was alleviated by increasing [Ca(2+)](L) or [Ca(2+)](C). Ca(2+) and Mg(2+) on opposite sides of the bilayer exhibited competitive effects on RYRs, indicating that they can compete via the pore for common sites. The data were accurately fitted by a model based on a tetrameric RYR structure with four Ca(2+)-sensing mechanisms on each subunit: activating luminal L-site (40-microM affinity for Mg(2+) and Ca(2+)), cytoplasmic A-site (1.2 microM for Ca(2+) and 60 microM for Mg(2+)), inactivating cytoplasmic I(1)-site (approximately 10 mM for Ca(2+) and Mg(2+)), and I(2)-site (1.2 microM for Ca(2+)). Activation of three or more subunits will cause channel opening. Mg(2+) inhibition occurs primarily by Mg(2+) displacing Ca(2+) from the L- and A-sites, and Mg(2+) fails to open the channel. The model predicts that under physiological conditions, SR load-dependent Ca(2+) release (1) is mainly determined by Ca(2+) displacement of Mg(2+) from the L-site as SR loading increases, and (2) depends on the properties of both luminal and cytoplasmic activation mechanisms.
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Affiliation(s)
- Derek R Laver
- School of Biomedical Sciences, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW 2308, Australia.
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