1
|
Lima MED, Martin-Eauclaire MF. The Toxins Purified fromTityus Serrulatus(Lutz & Mello)Venom. ACTA ACUST UNITED AC 2008. [DOI: 10.3109/15569549509019474] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
2
|
Kempner ES. Molecular size determination of enzymes by radiation inactivation. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 61:107-47. [PMID: 3281417 DOI: 10.1002/9780470123072.ch3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- E S Kempner
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, Maryland 20892
| |
Collapse
|
3
|
Affiliation(s)
- H Glossmann
- Institut für Biochemische Pharmakologie der Leopold-Franzens-Universität Innsbruck, Austria
| | | |
Collapse
|
4
|
Stocker M, Hirzel K, D'hoedt D, Pedarzani P. Matching molecules to function: neuronal Ca2+-activated K+ channels and afterhyperpolarizations. Toxicon 2004; 43:933-49. [PMID: 15208027 DOI: 10.1016/j.toxicon.2003.12.009] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2003] [Accepted: 12/06/2003] [Indexed: 11/21/2022]
Abstract
Potassium channels regulate the membrane excitability of neurons, play a major role in shaping action potentials, determining firing patterns and regulating neurotransmitter release, and thus significantly contribute to neuronal signal encoding and integration. This review focuses on the molecular and cellular basis for the specific function of small-conductance calcium-activated potassium channels (SK channels) in the nervous system. SK channels are activated by an intracellular increase of free calcium during action potentials. They mediate currents that modulate the firing frequency of neurons. Three SK channel subunits have been cloned and form channels, which are voltage-insensitive, activated by submicromolar intracellular calcium concentrations, and are blocked, with different affinities, by a number of toxins and organic compounds. Different neurons in the central and peripheral nervous system express distinct subsets of SK channel subunits. Recent progress has been made in relating cloned SK channels to their native counterparts. These findings argue in favour of regulatory mechanisms conferring to native SK channels with specific subunit compositions distinct and specific functional profiles in different neurons.
Collapse
Affiliation(s)
- Martin Stocker
- Wellcome Laboratory for Molecular Pharmacology, Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
| | | | | | | |
Collapse
|
5
|
Utkin YN. Photoactivatable derivatives of peptide and protein ligands in the study of neuroreceptor structure. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2000. [DOI: 10.1007/bf02758856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
6
|
|
7
|
Wadsworth JD, Torelli S, Doorty KB, Strong PN. Structural diversity among subtypes of small-conductance Ca2+-activated potassium channels. Arch Biochem Biophys 1997; 346:151-60. [PMID: 9328295 DOI: 10.1006/abbi.1997.0280] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
125I-Apamin and photolabile derivatives of the toxin have been used to investigate the binding properties and subunit composition of small conductance Ca2+-activated potassium channels (SK(Ca) channels) expressed on plasma membranes from rat brain, rabbit liver, or rat pheochromocytoma (PC12) cells. On all preparations, 125I-apamin recognized single classes of acceptor binding sites with similar high affinity (Kd approximately 3-6 pM). Gallamine, however, was found to readily discriminate between 125I-apamin acceptors present in these preparations, showing a maximal approx nine-fold difference in affinity for acceptors expressed by rabbit liver or PC12 cells. Affinity-labeling patterns revealed the expression of different hetero-oligomeric combinations of high (86 or 59 kDa) and low (33 or 30 kDa) molecular mass 125I-apamin-binding polypeptides, consistent with pharmacological differences. Alternative expression of either 86- or 59-kDa polypeptides appeared to be the most important factor influencing gallamine's affinity for SK(Ca) channel subtypes. Both high- and low-molecular-mass polypeptides are integral membrane proteins, the latter being glycosylated in a tissue-specific manner.
Collapse
Affiliation(s)
- J D Wadsworth
- Department of Paediatrics and Neonatal Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom
| | | | | | | |
Collapse
|
8
|
Doorty KB, Bevan S, Wadsworth JD, Strong PN. A novel small conductance Ca2+-activated K+ channel blocker from Oxyuranus scutellatus taipan venom. Re-evaluation of taicatoxin as a selective Ca2+ channel probe. J Biol Chem 1997; 272:19925-30. [PMID: 9242659 DOI: 10.1074/jbc.272.32.19925] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Taicatoxin, isolated from the venom of the Australian taipan snake Oxyuranus scutellatus, has been previously regarded as a specific blocker of high threshold Ca2+ channels in heart. Here we show that taicatoxin (in contrast to a range of other Ca2+ channel blockers) interacts with apamin-sensitive, small conductance, Ca2+-activated potassium channels on both chromaffin cells and in the brain. Taicatoxin displays high affinity recognition of 125I-apamin acceptor-binding sites, present on rat synaptosomal membranes (Ki = 1.45 +/- 0.22 nM) and also specifically blocks affinity-labeling of a 33-kDa 125I-apamin-binding polypeptide on rat brain membranes. Taicatoxin (50 nM) completely blocks apamin-sensitive after-hyperpolarizing slow tail K+ currents generated in rat chromaffin cells (mean block 97 +/- 3%, n = 12) while only partially reducing total voltage-dependent Ca2+ currents (mean block 12 +/- 4%, n = 6). In view of these findings, the use of taicatoxin as a specific ligand for Ca2+ channels should now be reconsidered.
Collapse
Affiliation(s)
- K B Doorty
- Neuromuscular Unit, Department of Paediatrics and Neonatal Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London W12 0NN, United Kingdom
| | | | | | | |
Collapse
|
9
|
Garcia ML, Hanner M, Knaus HG, Koch R, Schmalhofer W, Slaughter RS, Kaczorowski GJ. Pharmacology of potassium channels. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1997; 39:425-71. [PMID: 9160122 DOI: 10.1016/s1054-3589(08)60078-2] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- M L Garcia
- Department of Membrane Biochemistry and Biophysics, Merck Research Laboratories, Rahway, New Jersey 07065, USA
| | | | | | | | | | | | | |
Collapse
|
10
|
Wadsworth J, Doorty K, Strong P. Comparable 30-kDa apamin binding polypeptides may fulfill equivalent roles within putative subtypes of small conductance Ca(2+)-activated K+ channels. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32416-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
11
|
Knaus H, Folander K, Garcia-Calvo M, Garcia M, Kaczorowski G, Smith M, Swanson R. Primary sequence and immunological characterization of beta-subunit of high conductance Ca(2+)-activated K+ channel from smooth muscle. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32551-6] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
12
|
Garcia-Calvo M, Knaus HG, Garcia ML, Kaczorowski GJ, Kempner ES. Functional unit size of the charybdotoxin receptor in smooth muscle. Proc Natl Acad Sci U S A 1994; 91:4718-22. [PMID: 7515178 PMCID: PMC43859 DOI: 10.1073/pnas.91.11.4718] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Target inactivation analysis was used to determine the functional size of the charybdotoxin (ChTX) receptor in aortic and tracheal sarcolemmal membrane vesicles. This receptor has previously been shown to be an integral component of the high-conductance Ca2+-activated K+ (Maxi-K) channel in these smooth muscles. Exposure of either bovine aortic or bovine tracheal sarcolemma to high-energy irradiation results in disappearance of 125I-labeled ChTX binding activity as a monoexponential function of radiation dose; from these functions molecular masses of 88 +/- 10 kDa and 89 +/- 6 kDa, respectively, can be calculated. Similar results were obtained from radiation inactivation studies with the detergent-solubilized ChTX receptor from aortic sarcolemmal membranes. The effect of radiation on 125I-labeled ChTX binding is to decrease the number of functional ChTX receptors without affecting the affinity of receptors for the toxin, indicating that radiation is destroying, rather than altering, the binding site. The validity of the radiation inactivation technique in these membrane preparations is supported by data obtained in parallel experiments in which target sizes of the alpha 1 subunit of the L-type Ca2+ channel and 5'-nucleotidase were measured. The molecular masses determined for these entities are in excellent agreement with those expected from previous studies. The present data are discussed in terms of the recently determined subunit composition of the smooth muscle Maxi-K channel. In light of the target size, a single alpha beta subunit heterodimer complex could serve as the ChTX receptor.
Collapse
Affiliation(s)
- M Garcia-Calvo
- Department of Membrane Biochemistry and Biophysics, Merck Research Laboratories, Rahway, NJ 07065
| | | | | | | | | |
Collapse
|
13
|
Knaus H, Garcia-Calvo M, Kaczorowski G, Garcia M. Subunit composition of the high conductance calcium-activated potassium channel from smooth muscle, a representative of the mSlo and slowpoke family of potassium channels. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41720-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
14
|
Garcia-Calvo M, Knaus H, McManus O, Giangiacomo K, Kaczorowski G, Garcia M. Purification and reconstitution of the high-conductance, calcium-activated potassium channel from tracheal smooth muscle. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42402-1] [Citation(s) in RCA: 148] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
15
|
Sokol PT, Hu W, Yi L, Toral J, Chandra M, Ziai MR. Cloning of an apamin binding protein of vascular smooth muscle. JOURNAL OF PROTEIN CHEMISTRY 1994; 13:117-28. [PMID: 7912073 DOI: 10.1007/bf01891999] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The receptor for the bee venom derived neurotoxin, apamin, is widely believed to be an integral component of the small conductance calcium-activated potassium channel in many excitable cells. By affinity chromatography on immobilized apamin, a 78 kD apamin binding protein of the bovine brain synaptosomes was isolated. Antibodies were elicited against this protein and used to clone a cDNA from a porcine vascular smooth muscle expression library. This gene (Kcal 1.8) codes for a 438 amino protein with four potential transmembrane domains, one putative calcium binding site, a protein kinase C phosphorylation site, and a leucine zipper motif. Kcal 1.8 encoded protein has no significant sequence homologies with any known ion channels or receptors. Kcal 1.8 is likely to encode a protein associated with the small conductance calcium-activated potassium channel in vascular smooth muscle.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Antibodies, Monoclonal
- Apamin/metabolism
- Binding Sites
- Blotting, Northern
- Blotting, Western
- Brain/metabolism
- Calcium/metabolism
- Cattle
- Cell Line
- Chromatography, Affinity
- Cloning, Molecular/methods
- Electrophoresis, Polyacrylamide Gel
- Gene Library
- Humans
- Leucine Zippers
- Melanoma
- Molecular Sequence Data
- Molecular Weight
- Muscle, Smooth, Vascular/metabolism
- Neuroblastoma
- Poly A/analysis
- Poly A/biosynthesis
- Potassium Channels/biosynthesis
- Potassium Channels/chemistry
- Potassium Channels/isolation & purification
- Protein Structure, Secondary
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- Recombinant Proteins/biosynthesis
- Recombinant Proteins/chemistry
- Swine
- Synaptosomes/metabolism
- Tumor Cells, Cultured
Collapse
Affiliation(s)
- P T Sokol
- Department of Molecular Pharmacology, American Cyanamid Company, Lederle Laboratories, Pearl River, New York 10965
| | | | | | | | | | | |
Collapse
|
16
|
Shahidi S, Poronnik P, Barden JA, Cook DI. Structure-function relations of biotin derivatives of apamin. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1157:74-80. [PMID: 8388734 DOI: 10.1016/0304-4165(93)90080-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Apamin was biotinylated at various residues so as to produce an apamin derivative that was suitable for labelling apamin sensitive K+ channels. We labelled the sole histidine residue (His-18) of apamin with diazobenzoyl biocytin (DBB) and Lys-4 with NHS-biotin and NHS-XX-biotin. We found that at least two labelled species were produced by DBB. Proton NMR spectroscopy revealed that in addition to labelling the His-18, DBB labelled the Gln-16 and Gln-17 of apamin. Both NHS-biotin and NHS-XX-biotin appeared to specifically label Lys-4. To test the potency of these apamin derivatives, we developed an assay using apamin reversal of the adrenaline induced relaxation of the mouse ascending colon. The biological activity of the His-18 derivative was 46-fold less than that of native apamin. Biotinylation of Lys-4 with NHS-biotin reduced the activity by only 6-fold. The inclusion of a 14-carbon spacer between the Lys-4 and the biotin resulted in a derivative with only a 4-fold reduction in potency.
Collapse
Affiliation(s)
- S Shahidi
- Department of Physiology, University of Sydney, NSW, Australia
| | | | | | | |
Collapse
|
17
|
Garcia ML, Galvez A, Garcia-Calvo M, King VF, Vazquez J, Kaczorowski GJ. Use of toxins to study potassium channels. J Bioenerg Biomembr 1991; 23:615-46. [PMID: 1917911 DOI: 10.1007/bf00785814] [Citation(s) in RCA: 159] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Potassium channels comprise groups of diverse proteins which can be distinguished according to each member's biophysical properties. Some types of K+ channels are blocked with high affinity by specific peptidyl toxins. Three toxins, charybdotoxin, iberiotoxin, and noxiustoxin, which display a high degree of homology in their primary amino acid sequences, have been purified to homogeneity from scorpion venom. While charybdotoxin and noxiustoxin are known to inhibit more than one class of channel (i.e., several Ca(2+)-activated and voltage-dependent K+ channels), iberiotoxin appears to be a selective blocker of the high-conductance, Ca(2+)-activated K+ channel that is present in muscle and neuroendocrine tissue. A distinct class of small-conductance Ca(2+)-activated K+ channel is blocked by two other toxins, apamin and leiurotoxin-1, that share no sequence homology with each other. A family of homologous toxins, the dendrotoxins, have been purified from venom of various related species of snakes. These toxins inhibit several inactivating voltage-dependent K+ channels. Although molecular biology approaches have been employed to identify and characterize several species of voltage-gated K+ channels, toxins directed against a particular channel can still be useful in defining the physiological role of that channel in a particular tissue. In addition, for those K+ channels which are not yet successfully probed by molecular biology techniques, toxins can be used as biochemical tools with which to purify the target protein of interest.
Collapse
Affiliation(s)
- M L Garcia
- Department of Membrane Biochemistry and Biophysics, Merck Institute for Therapeutic Research, Rahway, New Jersey 07065
| | | | | | | | | | | |
Collapse
|
18
|
Labbé-Jullié C, Granier C, Albericio F, Defendini ML, Ceard B, Rochat H, Van Rietschoten J. Binding and toxicity of apamin. Characterization of the active site. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 196:639-45. [PMID: 2013287 DOI: 10.1111/j.1432-1033.1991.tb15860.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The structural features of apamin, a natural octadecapeptide from bee venom, enabling binding to its receptor and the expression of toxicity in mice, have been delineated by studying the effects on binding and toxicity of chemical modifications and amino acid substitutions in synthetic analogues. The results obtained indicate that the only hydrophobic residue, leucine at position 10, can be changed to alanine without a significant decrease in the specific activity. The need for a correct conformation has been established and also the importance of Gln-17 and the side chains of Arg-13 and Arg-14 (besides the charge effects). The interaction of apamin with its receptor, a calcium-activated potassium channel, is thus mediated by a precise topology around these three residues. Due to the ability to detect very low specific activities for some of the analogues, it has been shown that, individually, none of these interactions constitute an essential criteria for binding per se, but that their presence is necessary for the high specific activity of the toxin.
Collapse
Affiliation(s)
- C Labbé-Jullié
- Centre National de la Recherche Scientifique UA 1179, Faculté de Médecine Secteur Nord, Marseille, France
| | | | | | | | | | | | | |
Collapse
|
19
|
Leveque C, Marqueze B, Couraud F, Seagar M. Polypeptide components of the apamin receptor associated with a calcium activated potassium channel. FEBS Lett 1990; 275:185-9. [PMID: 2175714 DOI: 10.1016/0014-5793(90)81468-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Photoaffinity labeling of rat brain membranes with [125I]ANPAA-apamin incorporated radioactivity into polypeptides of 86 and 59 kDa and occasionally a more weakly labeled component of 45 kDa. These polypeptides were immunoprecipitated with anti-apamin antibodies and treated with glycosidases. Neither the 86 nor the 59 kDa polypeptide appeared to be N-glycosylated. Partial proteolytic mapping of affinity labeled polypeptides with chymotrypsin or V8 protease generated an identical pattern. These results suggest that the 59 and 45 kDa components are not additional subunits of an oligomeric protein but result from cleavage of the 86 kDa polypeptide.
Collapse
Affiliation(s)
- C Leveque
- Laboratoire de Biochimie, CNRS UA1179, Faculté de Médecine Nord, Marseille, France
| | | | | | | |
Collapse
|
20
|
|
21
|
Dreyer F. Peptide Toxins and Potassium Channels. Rev Physiol Biochem Pharmacol 1990. [DOI: 10.1007/978-3-662-41884-0_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
22
|
Abstract
Many venom toxins interfere with ion channel function. Toxins, as specific, high affinity ligands, have played an important part in purifying and characterizing many ion channel proteins. Our knowledge of potassium ion channel structure is meager because until recently, no specific potassium channel toxins were known, or identified as such. This review summarizes the sudden explosion of research on potassium channel toxins that has occurred in recent years. Toxins are discussed in terms of their structure, physiological and pharmacological properties, and the characterization of toxin binding sites on different subtypes of potassium ion channels.
Collapse
Affiliation(s)
- P N Strong
- Jerry Lewis Muscle Research Centre, Department of Paediatrics and Neonatal Medicine, Royal Postgraduate Medical School, London, U.K
| |
Collapse
|
23
|
Defendini ML, Bahraoui EM, Labbe-Jullie C, Regnier-Vigouroux A, el Ayeb M, van Rietschoten J, Rochat H, Granier C. Identification of antigenic residues on apamin recognized by polyclonal antibodies. Mol Immunol 1990; 27:37-44. [PMID: 1690348 DOI: 10.1016/0161-5890(90)90058-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The structural requirements for antigenic recognition of apamin--an 18-amino acid, disulfide-bridged peptide--by rabbit antibodies were defined using a set of 18 apamin analogs in a competition liquid-phase radioimmunoassay. Some residues contribute considerably to antigenic recognition, e.g. Ala10, Arg13, and others to a lesser extent, e.g. Arg14, Glu7 and Thr8. The N- and C-terminal moieties of apamin are less antigenically important. These findings suggest that a good part of antibody specificities are directed to the central tightly folded part of the molecule. They are consistent with the observation that in saturating conditions, labeled apamin can, on average, bind one specific Fab fragment.
Collapse
Affiliation(s)
- M L Defendini
- Laboratoire de Biochimie, CNRS URA 1179 INSERM U172, Faculté de Médecine Secteur Nord, Marseille, France
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Ruth P, Röhrkasten A, Biel M, Bosse E, Regulla S, Meyer HE, Flockerzi V, Hofmann F. Primary structure of the beta subunit of the DHP-sensitive calcium channel from skeletal muscle. Science 1989; 245:1115-8. [PMID: 2549640 DOI: 10.1126/science.2549640] [Citation(s) in RCA: 304] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Complementary DNAs for the beta subunit of the dihydropyridine-sensitive calcium channel of rabbit skeletal muscle were isolated on the basis of peptide sequences derived from the purified protein. The deduced primary structure is without homology to other known protein sequences and is consistent with the beta subunit being a peripheral membrane protein associated with the cytoplasmic aspect of the sarcolemma. The protein contains sites that might be expected to be preferentially phosphorylated by protein kinase C and guanosine 3',5'-monophosphate-dependent protein kinase. A messenger RNA for this protein appears to be expressed in brain.
Collapse
Affiliation(s)
- P Ruth
- Institut für Physiologische Chemie, Medizinische Fakultät, Homburg/Saar, Federal Republic of Germany
| | | | | | | | | | | | | | | |
Collapse
|
25
|
Marquèze B, Seagar MJ, Couraud F. Characterization of apamin-binding protein associated with a Ca2+ -activated K+ channel. JOURNAL OF PROTEIN CHEMISTRY 1989; 8:425-7. [PMID: 2551328 DOI: 10.1007/bf01674309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- B Marquèze
- Zentrum für Molekulare Biologie, Universität Heidelberg, FRG
| | | | | |
Collapse
|
26
|
Abstract
Several recently characterized toxins (apamin, charybdotoxin, dendrotoxin and noxiustoxin) are proving invaluable for establishing what kinds of potassium channel are expressed in neurones, and what the roles of the channels might be.
Collapse
|
27
|
Moczydlowski E, Lucchesi K, Ravindran A. An emerging pharmacology of peptide toxins targeted against potassium channels. J Membr Biol 1988; 105:95-111. [PMID: 2464066 DOI: 10.1007/bf02009164] [Citation(s) in RCA: 181] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Voltage-dependent ion channels are a difficult class of proteins to approach biochemically. Many such channels are present at low density in relevant tissues and exist as multiple subtypes that can be distinguished electrophysiologically. In particular, K channels appear to be a diverse family of proteins characterized by many different conductance properties, gating behaviors and regulatory phenomena. Fortunately, specific peptide toxins for K channels are present in the venoms of insects, scorpions, snakes and possibly other species. The available sequences of these peptides define several different families of toxins. Electrophysiological and radioligand binding studies suggest that these toxins can be used to distinguish subclasses of K channels that share similar toxin binding sites. The growing databank of sequence homologies for both toxins and channels is, in essence, a codebook for identifying common elements of structure and function. The continuing development of toxins as biochemical probes should help to uncover the molecular basis and physiological significance of K-channel diversity.
Collapse
Affiliation(s)
- E Moczydlowski
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510
| | | | | |
Collapse
|
28
|
Zemková H, Teisinger J, Vyskocil F. Inhibition of the electrogenic Na,K pump and Na,K-ATPase activity by tetraethylammonium, tetrabutylammonium, and apamin. J Neurosci Res 1988; 19:497-503. [PMID: 2838645 DOI: 10.1002/jnr.490190414] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The K+-induced hyperpolarization of Na-loaded mouse diaphragm muscle, enzymatic activity of Na,K-ATPase and 3H-ouabain binding to rat brain microsomes was measured in the presence of K+ channel blockers tetraethylammonium (TEA), tetrabutylammonium (TBA) and apamin. TBA, and to a lesser extent TEA in millimolar concentrations, inhibited the electrogenic effect of the Na,K pump, Na,K-ATPase activity, and 3H-ouabain binding. The inhibition of 3H-ouabain binding by TEA or TBA was more evident in the presence of ATP and Na+ ions. Apamin in nanomolar concentrations inhibited the electrogenic effect of Na,K pump and Na,K-ATPase but not the 3H-ouabain binding. The hyperpolarizing effects of insulin and NADH, but not that of noradrenaline, were also prevented by apamin. The inhibition of Na,K pump by TEA and TBA is apparently due to both competition with K+ for a binding site on the Na,K-ATPase and a reduction in the number of transporting sites. The site of action of apamin on Na,K-ATPase is different from that of tetra-alkylammonium compounds; it apparently decreases the turnover rate of the enzyme.
Collapse
Affiliation(s)
- H Zemková
- Institute of Physiology, Czechoslovak Academy of Sciences, Prague
| | | | | |
Collapse
|
29
|
Seagar MJ, Takahashi M, Catterall WA. Molecular properties of dihydropyridine-sensitive calcium channels. Ann N Y Acad Sci 1988; 522:162-75. [PMID: 2454051 DOI: 10.1111/j.1749-6632.1988.tb33352.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- M J Seagar
- Department of Pharmacology, University of Washington, Seattle 98195
| | | | | |
Collapse
|
30
|
de Lima ME, Couraud F, Lapied B, Pelhate M, Ribeiro Diniz C, Rochat H. Photoaffinity labeling of scorpion toxin receptors associated with insect synaptosomal Na+ channels. Biochem Biophys Res Commun 1988; 151:187-92. [PMID: 2450534 DOI: 10.1016/0006-291x(88)90577-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Photoreactive and radioiodinated derivatives of several scorpion toxins acting on insect Na+ channels were prepared without loss of their pharmacological activities. Photoaffinity experiments were carried out on a synaptosomal fraction from the nerve cord of the cockroach Periplaneta americana: with all toxin derivatives, a single specifically labeled band was obtained with a molecular weight of 188,000 +/- 12,000 (n = 17). These results indicate for the first time the molecular weight of the scorpion toxin receptor from the insect nervous system which is probably associated with voltage sensitive Na+ channels. One of these toxins, toxin VII from Tityus serrulatus venom, has been previously shown to be active both in mammals and in insects, in rat brain synaptosomes this toxin labeled a Mr = 31,000 +/- 4,000 band in contrast, to observations in the insect preparation.
Collapse
Affiliation(s)
- M E de Lima
- CNRS UA 1179, INSERM U 172, Laboratoire de Biochimie, Faculté de Médecine Nord, Marseille, France
| | | | | | | | | | | |
Collapse
|
31
|
Valdivia HH, Smith JS, Martin BM, Coronado R, Possani LD. Charybdotoxin and noxiustoxin, two homologous peptide inhibitors of the K+ (Ca2+) channel. FEBS Lett 1988; 226:280-4. [PMID: 2448164 DOI: 10.1016/0014-5793(88)81439-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We show that noxiustoxin (NTX), like charybdotoxin (CTX) described by others, affects Ca2+-activated K+ channels of skeletal muscle (K+(Ca2+) channels). Chemical characterization of CTX shows that it is similar to NTX. Although the amino-terminal amino acid of CTX is not readily available, the molecule was partially sequenced after CNBr cleavage. A decapeptide corresponding to the C-terminal region of NTX shows 60% homology to that of CTX, maintaining the cysteine residues at the same positions. While CTX blocks the K+ (Ca2+) channels with a Kd of 1-3 nM, for NTX it is approx. 450 nM. Both peptides can interact simultaneously with the same channel. NTX and CTX promise to be good tools for channel isolation.
Collapse
Affiliation(s)
- H H Valdivia
- Department of Physiology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030
| | | | | | | | | |
Collapse
|
32
|
|
33
|
Chapter 18 Molecular Properties of Voltage-Sensitive Calcium Channels. ACTA ACUST UNITED AC 1988. [DOI: 10.1016/s0070-2161(08)60908-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
34
|
Goh JW, Pennefather PS. Pharmacological and physiological properties of the after-hyperpolarization current of bullfrog ganglion neurones. J Physiol 1987; 394:315-30. [PMID: 2451018 PMCID: PMC1191963 DOI: 10.1113/jphysiol.1987.sp016872] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
1. The slowly decaying, calcium-dependent after-hyperpolarization (a.h.p.) that follows action potentials in bullfrog ganglion B cells has previously been shown to be generated by a potassium current called IAHP. We have recorded IAHP using a switched, single-electrode hybrid clamp where current-clamp mode was changed to voltage-clamp mode immediately after repolarization of a spike or the last spike of a train. 2. Reduction of extracellular calcium reduced the decay time of IAHP following a single spike. At all levels of extracellular calcium tested (0.5-4 mM), the decay time of IAHP was longer following a train of action potentials than following a single action potential. Thus, the time course of IAHP evoked by action potentials is a function of the calcium load induced by the action potentials. Conversely, agents that reduce the amount of IAHP activated without affecting its rate of decay, probably do not affect calcium influx. 3. Muscarine (2 or 10 microM) inhibits IAHP following an action potential by at most 30% and has no effect on decay rate of IAHP. These results suggest that muscarine has little or no effect on either calcium influx or sequestration. Decay of the a.h.p. is accelerated by muscarine but this effect is due to an increased leak conductance. 4. Charybdotoxin (CTX) between 4 and 20 nM, prolongs action potential duration in a manner consistent with blockade of the voltage- and calcium-dependent potassium current (Ic) involved in spike repolarization in these cells. This action is consistent with its reported action on analogous channels in other systems. However, CTX also reduces IAHP. Thus, in bullfrog ganglion neurones, two distinct calcium-dependent potassium currents exhibit a comparable sensitivity to CTX. This cannot be due to a decreased influx of calcium because the decay rate of IAHP following an action potential is unchanged. The action of CTX was observed with both crude and purified preparations of CTX. 5. Apamin (25 nM) and (+)-tubocurarine (concentration giving 50% of maximal inhibition = 20 microM) block IAHP without affecting action potential duration. The action of (+)-tubocurarine is more readily reversible than apamin. Approximately 20% of IAHP is resistant to blockade by either apamin or (+)-tubocurarine. 6. Muscarine was used to block the M-current (IM) selectively and (+)-tubocurarine was used to inhibit IAHP selectively. Both currents were shown to contribute to spike frequency adaptation. Inhibition of both IM and IAHP has a synergistic action to increase repetitive firing.
Collapse
Affiliation(s)
- J W Goh
- Faculty of Pharmacy, University of Toronto, ON, Canada
| | | |
Collapse
|
35
|
Marquèze B, Seagar MJ, Couraud F. Photoaffinity labeling of the K+-channel-associated apamin-binding molecule in smooth muscle, liver and heart membranes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 169:295-8. [PMID: 2446869 DOI: 10.1111/j.1432-1033.1987.tb13611.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
High-affinity binding sites for mono[125I]iodoapamin were detected in membranes (Kd = 59 pM, Bmax = 24 fmol/mg protein) and cultured cells (Kd = 69 pM, Bmax = 2.8 fmol/mg protein) from rat heart and in membranes from guinea-pig ileum (Kd = 67 pM, Bmax 42 fmol/mg protein) and liver (Kd = 15 pM, Bmax = 43 fmol/mg protein). Binding was stimulated by K+ ions (K0.5 = 0.3-0.5 mM). Covalent labeling with arylazide [125I]iodoapamin derivatives showed that smooth muscle, liver and heart binding molecules are associated with a 85-87-kDa polypeptide. A second strongly labeled 57-kDa component was identified in liver membranes only.
Collapse
Affiliation(s)
- B Marquèze
- Laboratoire de Biochimie, Centre National de la Recherche Scientifique Unité Associée 1179, Marseille-France
| | | | | |
Collapse
|
36
|
O'Grady SM, Palfrey HC, Field M. Characteristics and functions of Na-K-Cl cotransport in epithelial tissues. THE AMERICAN JOURNAL OF PHYSIOLOGY 1987; 253:C177-92. [PMID: 3303961 DOI: 10.1152/ajpcell.1987.253.2.c177] [Citation(s) in RCA: 276] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
This review summarizes our present understanding of Na-K-Cl cotransport and its physiological role in absorption and secretion of electrolytes and water in epithelial tissues. In the past several years an extensive literature about this cotransporter has developed due to its widespread distribution in a variety of cell types and its essential role in fluid and electrolyte transport in several epithelial tissues. We summarize this literature and speculate on the future characterization of this transport system. Although this review focuses on cotransport as it relates to absorptive and secretory processes in epithelia, important information concerning the pharmacology, stoichiometry, and regulation of Na-K-Cl cotransport in nonepithelial systems (i.e., erythrocytes, fibroblasts, squid axon, etc.) has been included to supplement areas that are less well established in the epithelial literature.
Collapse
|
37
|
Takahashi M, Seagar MJ, Jones JF, Reber BF, Catterall WA. Subunit structure of dihydropyridine-sensitive calcium channels from skeletal muscle. Proc Natl Acad Sci U S A 1987; 84:5478-82. [PMID: 2440051 PMCID: PMC298881 DOI: 10.1073/pnas.84.15.5478] [Citation(s) in RCA: 348] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Purified dihydropyridine-sensitive calcium channels from rabbit transverse-tubule membranes consist of three noncovalently associated classes of subunits: alpha (167 kDa), beta (54 kDa), and gamma (30 kDa). Cleavage of disulfide bonds reveals two distinct alpha polypeptides and an additional component, delta. The alpha 1 subunit, a 175-kDa polypeptide that is not N-glycosylated, contains the dihydropyridine binding site, cAMP-dependent protein kinase phosphorylation site(s), and substantial hydrophobic domain(s). alpha 2, a 143-kDa glycoprotein, has none of the properties characteristic of alpha 1 but binds lectins and contains about 25% N-linked carbohydrate. alpha 2 is disulfide-linked to delta, a 24- to 27-kDa glycopeptide. beta (54 kDa) contains a cAMP-dependent phosphorylation site but is not N-glycosylated and does not have a hydrophobic domain. gamma (30 kDa) has a carbohydrate content of about 30% and extensive hydrophobic domain(s). Precipitation with affinity-purified anti-alpha 1 antibodies or alpha 2-specific lentil lectin-agarose demonstrated that alpha 1 alpha 2 beta gamma delta behaves as a complex in the presence of digitonin or 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, whereas the alpha 2 delta complex dissociates from alpha 1 beta gamma in the presence of Triton X-100. A model for subunit interaction and membrane insertion is proposed on the basis of these observations.
Collapse
|