51
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Braun AP. A novel mechanism for chemosensory transduction in insects. Channels (Austin) 2010; 2:158. [PMID: 18797188 DOI: 10.4161/chan.2.3.6245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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52
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Braun AP. Delivering the goods: Activity-induced exocytosis and AMPA receptor insertion within a post-synaptic membrane compartment depends on syntaxin 4. Channels (Austin) 2010; 4:137-8. [PMID: 20814225 DOI: 10.4161/chan.12649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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53
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Braun AP. A new "opening" act on the BK channel stage: identification of LRRC26 as a novel BK channel accessory subunit that enhances voltage-dependent gating. Channels (Austin) 2010; 4:249-50. [PMID: 21057223 DOI: 10.4161/chan.4.4.13330] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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54
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Braun AP. Coordinate regulation of stretch-activated channels and myogenic tone by polycystins 1 and 2. Channels (Austin) 2010; 4:1-2. [PMID: 20368689 DOI: 10.4161/chan.4.1.11537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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55
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Braun AP, Raqeeb A, Sheng J. The Purinergic Agonists ATP and UTP Act Predominantly via P2Y Receptors in Human Vascular Endothelial Cells. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.593.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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56
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Liao C, Breemen C, Braun AP, Cole WC. Reverse mode sodium‐calcium exchange (NCXrev) facilitated by co‐localization of the exchanger with TRPC channels contributes to Ca2+ influx and ER Ca2+ store refilling during agonist stimulation of endothelial cells. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.819.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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57
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Yang Y, Ella SR, Braun AP, Korthuis RJ, Davis MJ, Hill MA. Manipulation of smooth muscle BK
Ca
using subunit directed siRNA. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.777.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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58
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Braun AP. Cooperative interactions between subunits regulate gating in holo-proton conductive channels. Channels (Austin) 2010; 4:12111. [PMID: 21228637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023] Open
Abstract
See also: Tombola F, Ulbrich MH, Kohout SC, Isacoff EY. The opening of the two pores of the Hv1 voltage-gated proton channel is tuned by cooperativity. Nat Struct Mol Biol 2010; 17:44-50; PMID: 20023640; DOI: 10.1038/nsmb.1738.
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Hill MA, Yang Y, Ella SR, Davis MJ, Braun AP. Large conductance, Ca2+-activated K+ channels (BKCa) and arteriolar myogenic signaling. FEBS Lett 2010; 584:2033-42. [PMID: 20178789 DOI: 10.1016/j.febslet.2010.02.045] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Accepted: 02/15/2010] [Indexed: 12/22/2022]
Abstract
Myogenic, or pressure-induced, vasoconstriction is critical for local blood flow autoregulation. Underlying this vascular smooth muscle (VSM) response are events including membrane depolarization, Ca(2+) entry and mobilization, and activation of contractile proteins. Large conductance, Ca(2+)-activated K(+) channel (BK(Ca)) has been implicated in several of these steps including, (1) channel closure causing membrane depolarization, and (2) channel opening causing hyperpolarization to oppose excessive pressure-induced vasoconstriction. As multiple mechanisms regulate BK(Ca) activity (subunit composition, membrane potential (Em) and Ca(2+) levels, post-translational modification) tissue level diversity is predicted. Importantly, heterogeneity in BK(Ca) channel activity may contribute to tissue-specific differences in regulation of myogenic vasoconstriction, allowing local hemodynamics to be matched to metabolic requirements. Knowledge of such variability will be important to exploiting the BK(Ca) channel as a therapeutic target and understanding systemic effects of its pharmacological manipulation.
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60
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Braun AP. Single particle imaging of a mammalian BK channel: extending primary sequence to tertiary structure. Channels (Austin) 2009; 3:299-300. [PMID: 19934644 DOI: 10.4161/chan.3.5.10269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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61
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Braun AP. Convergent signaling events underlie dopamine-mediated inhibition of CaV3.2 T-type calcium channels. Channels (Austin) 2009; 3:381-2. [PMID: 20026912 DOI: 10.4161/chan.3.6.10877] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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62
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Yang Y, Wu X, Gui P, Wu J, Sheng JZ, Ling S, Braun AP, Davis GE, Davis MJ. Alpha5beta1 integrin engagement increases large conductance, Ca2+-activated K+ channel current and Ca2+ sensitivity through c-src-mediated channel phosphorylation. J Biol Chem 2009; 285:131-41. [PMID: 19887442 DOI: 10.1074/jbc.m109.033506] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Large conductance, calcium-activated K(+) (BK) channels are important regulators of cell excitability and recognized targets of intracellular kinases. BK channel modulation by tyrosine kinases, including focal adhesion kinase and c-src, suggests their potential involvement in integrin signaling. Recently, we found that fibronectin, an endogenous alpha5beta1 integrin ligand, enhances BK channel current through both Ca(2+)- and phosphorylation-dependent mechanisms in vascular smooth muscle. Here, we show that macroscopic currents from HEK 293 cells expressing murine BK channel alpha-subunits (mSlo) are acutely potentiated following alpha5beta1 integrin activation. The effect occurs in a Ca(2+)-dependent manner, 1-3 min after integrin engagement. After integrin activation, normalized conductance-voltage relations for mSlo are left-shifted at free Ca(2+) concentrations >or=1 microm. Overexpression of human c-src with mSlo, in the absence of integrin activation, leads to similar shifts in mSlo Ca(2+) sensitivity, whereas overexpression of catalytically inactive c-src blocks integrin-induced potentiation. However, neither integrin activation nor c-src overexpression potentiates current in BK channels containing a point mutation at Tyr-766. Biochemical tests confirmed the critical importance of residue Tyr-766 in integrin-induced channel phosphorylation. Thus, BK channel activity is enhanced by alpha5beta1 integrin activation, likely through an intracellular signaling pathway involving c-src phosphorylation of the channel alpha-subunit at Tyr-766. The net result is increased current amplitude, enhanced Ca(2+) sensitivity, and rate of activation of the BK channel, which would collectively promote smooth muscle hyperpolarization in response to integrin-extracellular matrix interactions.
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Braun AP. Alternative splicing of TRIP8b diversifies its actions as an accessory subunit of neuronal HCN channels. Channels (Austin) 2009; 3:217-8. [PMID: 19690453 DOI: 10.4161/chan.3.4.9620] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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64
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Braun AP. Re-evaluating membrane transport processes: new insights and appreciation of protein behavior. Channels (Austin) 2009; 3:143. [PMID: 19556861 DOI: 10.4161/chan.3.3.9256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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65
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Braun AP. Distinct post-translational modifications regulate BK channel activity: the interplay between protein palmitoylation and phosphorylation. Channels (Austin) 2009; 3:144-5. [PMID: 19556862 DOI: 10.4161/chan.3.3.9257] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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66
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Braun AP. Cloning and expression of a calcium-activated chloride channel reveal a novel protein candidate. Channels (Austin) 2009; 2:393-4. [PMID: 19106617 DOI: 10.4161/chan.2.6.7648] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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67
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Yang Y, Murphy TV, Ella SR, Grayson TH, Haddock R, Hwang YT, Braun AP, Peichun G, Korthuis RJ, Davis MJ, Hill MA. Heterogeneity in function of small artery smooth muscle BKCa: involvement of the beta1-subunit. J Physiol 2009; 587:3025-44. [PMID: 19359368 DOI: 10.1113/jphysiol.2009.169920] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Arteriolar myogenic vasoconstriction occurs when increased stretch or membrane tension leads to smooth muscle cell depolarization and opening of voltage-gated Ca2+ channels. To prevent positive feedback and excessive pressure-induced vasoconstriction, studies in cerebral artery smooth muscle have suggested that activation of large conductance, Ca2+-activated K+ channels (BKCa) provides an opposing hyperpolarizing influence reducing Ca2+ channel activity. We have hypothesized that this mechanism may not equally apply to all vascular beds. To establish the existence of such heterogeneity in vascular reactivity, studies were performed on rat vascular smooth muscle (VSM) cells from cremaster muscle arterioles and cerebral arteries. Whole cell K+ currents were determined at pipette [Ca2+] of 100 nM or 5 microM in the presence and absence of the BKCa inhibitor, iberiotoxin (IBTX; 0.1 microM). Similar outward current densities were observed for the two cell preparations at the lower pipette Ca2+ levels. At 5 microM Ca2+, cremaster VSM showed a significantly (P < 0.05) lower current density compared to cerebral VSM (34.5 +/- 1.9 vs 45.5 +/- 1.7 pA pF(-1) at +70 mV). Studies with IBTX suggested that the differences in K+ conductance at 5 microM intracellular [Ca2+] were largely due to activity of BKCa. 17beta-Oestradiol (1 microM), reported to potentiate BKCa current via the channel's beta-subunit, caused a greater effect on whole cell K+ currents in cerebral vessel smooth muscle cells (SMCs) compared to those of cremaster muscle. In contrast, the alpha-subunit-selective BKCa opener, NS-1619 (20 microM), exerted a similar effect in both preparations. Spontaneously transient outward currents (STOCs) were more apparent (frequency and amplitude) and occurred at more negative membrane potentials in cerebral compared to cremaster SMCs. Also consistent with decreased STOC activity in cremaster SMCs was an absence of detectable Ca2+ sparks (0 of 76 cells) compared to that in cerebral SMCs (76 of 105 cells). Quantitative PCR showed decreased mRNA expression for the beta1 subunit and a decrease in the beta1:alpha ratio in cremaster arterioles compared to cerebral vessels. Similarly, cremaster arterioles showed a decrease in total BKCa protein and the beta1:alpha-subunit ratio. The data support vascular heterogeneity with respect to the activity of BKCa in terms of both beta-subunit regulation and interaction with SR-mediated Ca2+ signalling.
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Braun AP, Sheng J, Ella S, Davis MJ, Hill MA. Exploiting the cellular actions of SKCa and IKCa channels to manipulate endothelial function and vascular tone. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.627.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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69
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Braun AP. Mapping the route of ion conduction in a toxin-modified Na/K pump-channel. Channels (Austin) 2009; 3:75-6. [DOI: 10.4161/chan.3.2.8670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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70
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Gibbs SJ, Barren B, Beck KE, Proft J, Zhao X, Noskova T, Braun AP, Artemyev NO, Braun JEA. Hsp40 couples with the CSPalpha chaperone complex upon induction of the heat shock response. PLoS One 2009; 4:e4595. [PMID: 19242542 PMCID: PMC2643527 DOI: 10.1371/journal.pone.0004595] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Accepted: 01/13/2009] [Indexed: 01/22/2023] Open
Abstract
In response to a conditioning stress, the expression of a set of molecular chaperones called heat shock proteins is increased. In neurons, stress-induced and constitutively expressed molecular chaperones protect against damage induced by ischemia and neurodegenerative diseases, however the molecular basis of this protection is not known. Here we have investigated the crosstalk between stress-induced chaperones and cysteine string protein (CSPα). CSPα is a constitutively expressed synaptic vesicle protein bearing a J domain and a cysteine rich “string” region that has been implicated in the long term functional integrity of synaptic transmission and the defense against neurodegeneration. We have shown previously that the CSPα chaperone complex increases isoproterenol-mediated signaling by stimulating GDP/GTP exchange of Gαs. In this report we demonstrate that in response to heat shock or treatment with the Hsp90 inhibitor geldanamycin, the J protein Hsp40 becomes a major component of the CSPα complex. Association of Hsp40 with CSPα decreases CSPα-CSPα dimerization and enhances the CSPα-induced increase in steady state GTP hydrolysis of Gαs. This newly identified CSPα-Hsp40 association reveals a previously undescribed coupling of J proteins. In view of the crucial importance of stress-induced chaperones in the protection against cell death, our data attribute a role for Hsp40 crosstalk with CSPα in neuroprotection.
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Jones PP, Braun AP. Store operated Ca2+ entry (SOCE): from structure to function. Channels (Austin) 2009; 3:1-2. [PMID: 19221508 DOI: 10.4161/chan.3.1.7983] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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72
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Rosales-Hernandez A, Beck KE, Zhao X, Braun AP, Braun JEA. RDJ2 (DNAJA2) chaperones neural G protein signaling pathways. Cell Stress Chaperones 2009; 14:71-82. [PMID: 18595009 PMCID: PMC2673899 DOI: 10.1007/s12192-008-0056-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 05/28/2008] [Indexed: 12/11/2022] Open
Abstract
A number of structurally divergent proteins with J domains, called J proteins, interact with and activate the ATPase of Hsp70s, thereby harnessing the ATPase activity for conformational work on target proteins. The precise role of most mammalian J proteins remains undefined. In this paper, we demonstrate that transient expression of the J protein, Rdj2, in HEK 293 cells increased cellular cyclic adenosine monophosphate (cAMP) levels in the presence of the beta-adrenergic agonist isoproterenol. In CNS-derived catecholaminergic neuronal cell line (CAD) neuroblastoma cells, expression of Rdj2 increased isoproterenol-stimulated phosphorylation of cAMP response element binding protein (CREB). Moreover, we have characterized the binding properties of Rdj2 and observed a direct interaction between Rdj2 and receptor-coupled trimeric GTP-binding proteins (G proteins). We further show that the composition of the Rdj2-chaperone complex and the cysteine string protein (CSPalpha)-chaperone complex, another J protein, is distinct. Our data demonstrate that Rdj2 modulates G protein signaling and further suggest that chaperoning G proteins is an emerging theme of the J protein network.
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Sheng JZ, Ella S, Davis MJ, Hill MA, Braun AP. Openers of SKCa and IKCa channels enhance agonist-evoked endothelial nitric oxide synthesis and arteriolar vasodilation. FASEB J 2008; 23:1138-45. [PMID: 19074509 DOI: 10.1096/fj.08-120451] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recent data have led us to hypothesize that selective activation of endothelial small- and/or intermediate-conductance, calcium-activated potassium channels (SK(Ca) and IK(Ca) channels, respectively) by the opener compounds NS309 and DCEBIO would augment stimulated nitric oxide (NO) synthesis and vasodilation in resistance arteries. Experimentally, ATP-evoked changes in membrane potential, cytosolic Ca(2+), and NO synthesis were recorded by patch clamp and microfluorimetry in single human endothelial cells. Agonist-evoked inhibition of myogenic tone in isolated, pressurized arterioles from rat cremaster skeletal muscle was analyzed by video microscopy. NS309 and DCEBIO enhanced ATP-evoked membrane hyperpolarization and cytosolic Ca(2+) transients, along with acute NO synthesis in isolated endothelial cells. The acetylcholine-mediated inhibition of myogenic tone (IC(50)=237 nM) was left-shifted in the presence of NS309 and DCEBIO (10, 100, and 1000 nM) to IC(50) values of 101, 78, and 43 nM; endothelial denudation inhibited this drug effect. L-NAME attenuated the acetylcholine-induced inhibition of myogenic tone but did not interfere with NS309 and DCEBIO-evoked vasodilation. Collectively, our data demonstrate that drug-induced enhancement of endothelial SK(Ca) and IK(Ca) channel activities represents a novel cellular mechanism to increase vasodilation of small-resistance arterioles, thereby highlighting these channels as potential therapeutic targets in cardiovascular disease states associated with compromised NO signaling.
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Braun AP. A novel PIP2-binding protein acts to enhance TRP channel activity. Channels (Austin) 2008; 2:228. [PMID: 18769146 DOI: 10.4161/chan.2.4.6872] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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75
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Braun AP. The surprising proton channel: novel insights into its structure and function. Channels (Austin) 2008; 2:227. [PMID: 18769143 DOI: 10.4161/chan.2.4.6871] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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