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© The Rockefeller University Press,
0021-9525/1999//203 $5.00
The Journal of Cell Biology, Volume 146, Number 1,
, 1999 203-218
Original Article |
-Bungarotoxin Receptors Contain
7 Subunits in Two Different Disulfide-Bonded Conformations
wgreen{at}midway.uchicago.edu
Neuronal nicotinic
7 subunits assemble into cell-surface complexes that neither function nor bind
-bungarotoxin when expressed in tsA201 cells. Functional
-bungarotoxin receptors are expressed if the membrane-spanning and cytoplasmic domains of the
7 subunit are replaced by the homologous regions of the serotonin-3 receptor subunit. Bgt-binding surface receptors assembled from chimeric
7/serotonin-3 subunits contain subunits in two different conformations as shown by differences in redox state and other features of the subunits. In contrast,
7 subunit complexes in the same cell line contain subunits in a single conformation. The appearance of a second
7/serotonin-3 subunit conformation coincides with the formation of
-bungarotoxin–binding sites and intrasubunit disulfide bonding, apparently within the
7 domain of the
7/serotonin-3 chimera. In cell lines of neuronal origin that produce functional
7 receptors,
7 subunits undergo a conformational change similar to
7/serotonin-3 subunits.
7 subunits, thus, can fold and assemble by two different pathways. Subunits in a single conformation assemble into nonfunctional receptors, or subunits expressed in specialized cells undergo additional processing to produce functional,
-bungarotoxin–binding receptors with two
7 conformations. Our results suggest that
7 subunit diversity can be achieved postranslationally and is required for functional homomeric receptors.
Key Words:
-bungarotoxin
7 subunits nicotinic receptors protein folding disulfide bonds
© 1999 The Rockefeller University Press
1.used in this paper: 5HT, 5-hydroxytryptamine (serotonin); ACh, acetylcholine; AChR, acetylcholine receptor; Bgt,
-bungarotoxin; BgtR,
-bungarotoxin receptor; HA, hemagglutinin; NEM, N-ethylmaleimide; TMR-Bgt,
-bungarotoxin tetramethylrhodamine Sergey Rakhilin's present address is Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, NY 10021.
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