spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online August 31, 2004
Journal of Experimental Biology 207, 3581-3590 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01204
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tierney, M. L.
Right arrow Articles by Howitt, S. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tierney, M. L.
Right arrow Articles by Howitt, S. M.

Phylogenetic conservation of disulfide-linked, dimeric acetylcholine receptor pentamers in southern ocean electric rays

M. L. Tierney1,*, K. E. Osborn1, P. J. Milburn2, M. H. B. Stowell3 and S. M. Howitt1

1 School of Biochemistry & Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
2 John Curtin School of Medical Research, Australian National University, Canberra, ACT 0200, Australia
3 MCD Biology, University of Colorado, Boulder, CO 80309, USA

* Author for correspondence (e-mail: louise.tierney{at}anu.edu.au)

Accepted 15 July 2004

Intact acetylcholine receptors have been purified on a novel affinity resin from three electric fish endemic to Australian waters. Their binding properties and morphology are compared with those of their northern hemisphere homolog, Torpedo marmorata. All four exhibit apparent dissociation constants, Kd, in the nanomolar range for the snake neurotoxin {alpha}-bungarotoxin and have a distinctive rosette-like appearance when viewed in negative stain under the electron microscope. Furthermore, these rosettes are paired, indicating that acetylcholine receptors from southern ocean electric fish exist as dimers, in the same fashion as their northern hemisphere counterparts. The cDNAs of the receptor's four subunits were sequenced from Hypnos monopterigium and the northern hemisphere counterpart, Torpedo marmorata, while cDNAs from only two subunits, {alpha} and {delta}, were able to be sequenced from Narcine tasmaniensis. The penultimate amino acid in the {delta} subunit of each of the newly sequenced fish species is a cysteine residue. Its conservation suggests that the mechanism for the observed dimerization of acetylcholine receptors is disulfide bond formation between the {delta} subunit of adjacent receptors, analogous to acetylcholine receptor dimers observed in other electric fish. It appears that this mechanism for receptor clustering is unique to acetylcholine receptors packed and organized in the specialized organs of electric fish. Alignment of the deduced protein sequences with the equivalent sequences from Torpedo californica and humans reveals a high degree of homology.

Key words: acetylcholine receptor, ligand-gated ion channel, electric fish, dimer, clustering, Torpedo macneilli, Torpedo marmorata, Hypnos monopterigium, Narcine tasmaniensis






© The Company of Biologists Ltd 2004