J. Biol. Chem., Vol. 263, Issue 12, 5550-5554, Apr, 1988
Sodium-dependent inhibition of the epithelial sodium channel by an arginyl-specific reagent
H Garty, O Yeger and C Asher
Department of Membrane Research, Weizmann Institute of Science, Rehovot, Israel.
Effects of the arginyl- and lysyl-specific reagent phenylglyoxal (PGO) on
the epithelial Na+ channel were evaluated by measuring the amiloride-
blockable 22Na+ fluxes in membrane vesicles derived from the toad bladder
epithelium. Incubating whole cells or isolated membranes with PGO readily
and irreversibly blocked the channel-mediated tracer flux. Na+ ions present
during the interaction of membranes with PGO could protect channels from
inactivation by PGO. This effect required the presence of Na+ at the
luminal side of the membrane and was characterized by an IC50 of 79 mM Na+.
Amiloride, too, could desensitize channels to PGO, but its effect was
significant only when whole cells were interacted with the
protein-modifying reagent. The data are compatible with a model in which
the conductive path of the channel contains a functional arginine, possibly
forming a salt bridge with a carboxylic group, which is involved in Na+
translocation and amiloride binding. It was also shown that the
augmentation of transport induced by incubating whole cells in Ca2+-free
solution (Garty, H., and Asher, C. (1985) J. Biol. Chem. 260, 8330-8335)
involves the activation or recruitment of channels that are not vulnerable
to PGO prior to incubation.
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