title: Characterization of contryphans from Conus loroisii and Conus amadis that target calcium channels.
abstract: Distinctly different effects of two closely related contryphans have been demonstrated on voltage-activated Ca(2+) channels. The peptides Lo959 and Am975 were isolated from Conus loroisii, a vermivorous marine snail and Conus amadis, a molluscivore, respectively. The sequences of Lo959 and Am975 were deduced by mass spectrometric sequencing (MALDI-MS/MS) and confirmed by chemical synthesis. The sequences of Lo959, GCP(D)WDPWC-NH(2) and Am975, GCO(D)WDPWC-NH(2) (O: 4-trans-hydroxyproline: Hyp), differ only at residue 3; Pro in Lo959, Hyp in Am975, which is identical to contryphan-P, previously isolated from Conus purpurascens, a piscivore; while Lo959 is a novel peptide. Both Lo959 and Am975 undergo slow conformational interconversion under reverse-phase chromatographic conditions, a characteristic feature of all contryphans reported thus far. Electrophysiological studies performed using dorsal root ganglion neurons reveal that both peptides target high voltage-activated Ca(2+) channels. While Lo959 increases the Ca(2+) current, Am975 causes inhibition. The results establish that subtle sequence effects, which accompany post-translational modifications in Conus peptides, can have dramatic effects on target ion channels.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
authors.forename: V
authors.initials: V
authors.lastname: Sabareesh
authors.forename: K Hanumae
authors.initials: KH
authors.lastname: Gowd
authors.forename: P
authors.initials: P
authors.lastname: Ramasamy
authors.forename: S
authors.initials: S
authors.lastname: Sudarslal
authors.forename: K S
authors.initials: KS
authors.lastname: Krishnan
authors.forename: S K
authors.initials: SK
authors.lastname: Sikdar
authors.forename: P
authors.initials: P
authors.lastname: Balaram
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D020916:Conotoxins / Q000737:chemistry*; D052078:Conus Snail / Q000737:chemistry*; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000737:chemistry* / Q000235:genetics*; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: C519180:Am975 protein, Conus amadis; D015220:Calcium Channels; D020916:Conotoxins; C519179:Lo959 protein, Conus loroisii; D010455:Peptides; D010456:Peptides, Cyclic; C102355:contryphan