Novel omega-conotoxins from Conus catus discriminate among neuronal calcium channel subtypes.
omega-Conotoxins selective for N-type calcium channels are useful in the management of severe pain. In an attempt to expand the therapeutic potential of this class, four new omega-conotoxins (CVIA-D) have been discovered in the venom of the piscivorous cone snail, Conus catus, using assay-guided fractionation and gene cloning. Compared with other omega-conotoxins, CVID has a novel loop 4 sequence and the highest selectivity for N-type over P/Q-type calcium channels in radioligand binding assays. CVIA-D also inhibited contractions of electrically stimulated rat vas deferens. In electrophysiological studies, omega-conotoxins CVID and MVIIA had similar potencies to inhibit current through central (alpha(1B-d)) and peripheral (alpha(1B-b)) splice variants of the rat N-type calcium channels when coexpressed with rat beta(3) in Xenopus oocytes. However, the potency of CVID and MVIIA increased when alpha(1B-d) and alpha(1B-b) were expressed in the absence of rat beta(3), an effect most pronounced for CVID at alpha(1B-d) (up to 540-fold) and least pronounced for MVIIA at alpha(1B-d) (3-fold). The novel selectivity of CVID may have therapeutic implications. (1)H NMR studies reveal that CVID possesses a combination of unique structural features, including two hydrogen bonds that stabilize loop 2 and place loop 2 proximal to loop 4, creating a globular surface that is rigid and well defined.
Lewis
R J
RJ
Centre for Drug Design and Development (3D Centre), Institute for Molecular Bioscience, Department of Physiology and Pharmacology, CSIRO Tropical Agriculture, and Queensland Agricultural Biotechnology Centre (QDPI), Australia. r.lewis@mailbox.uq.edu.au
Nielsen
K J
KJ
Craik
D J
DJ
Loughnan
M L
ML
Adams
D A
DA
Sharpe
I A
IA
Luchian
T
T
Adams
D J
DJ
Bond
T
T
Thomas
L
L
Jones
A
A
Matheson
J L
JL
Drinkwater
R
R
Andrews
P R
PR
Alewood
P F
PF
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006860:Hydrogen Bonding; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010452:Peptide Biosynthesis; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012908:Snails; D013997:Time Factors; D014649:Vas Deferens / Q000378:metabolism; D014982:Xenopus laevis; D020960:omega-Conotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018076:DNA, Complementary; D007477:Ions; D010455:Peptides; D020033:Protein Isoforms; D012333:RNA, Messenger; D020960:omega-Conotoxins; C078452:ziconotide