Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 342, Issue 1, Pages 333-343Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2004.06.092
Keywords
assembly; ligand-gated ion channels; protein-protein interactions; quaternary structure; Xenopus oocytes
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Of the three major classes of ligand-gated ion channels, nicotinic receptors and ionotropic glutamate receptors are known to be organized as pentamers and tetramers, respectively. The architecture of the third class, P2X receptors, is under debate, although evidence for a trimeric assembly is accumulating. Here we provide biochemical evidence that in addition to the rapidly desensitising P2X(1) and P2X(3) receptors, the slowly desensitising subtypes P2X(2), P2X(4), and P2X(5) are trimers of identical subunits. Similar (heteromeric) P2X subunits also formed trimers, as shown for co-expressed P2X(1) and P2X(2) subunits, which assembled efficiently to a P2X(1) (+ 2) receptor that was exported to the plasma membrane. In contrast, P2X(6) subunits, which are incapable of forming functional homomeric channels in Xenopus oocytes, were retained in the ER as apparent tetramers and high molecular mass aggregates. Altogether, we conclude from these data that a trimeric architecture is the structural hallmark of functional homomeric and heteromeric P2X receptors. (C) 2004 Elsevier Ltd. All rights reserved.
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