Effects of thiol modification and Ca/sup + +/ on agonist-specific state transitions of nicotinic acetylcholine receptor from Torpedo californica electroplax

Journal Article · Mon Jan 01 04:00:00 EST 1979 · Life Sci.; (United States)

DOI:https://doi.org/10.1016/0024-3205(79)90241-8· OSTI ID:5297121

Miller, J V; Lukas, R J; Bennett, E L

The agonist binding affinity of nicotinic acetylcholine receptor (nAChR) from Torpedo californica electroplax, as inferred from ability of agonist to inhibit specific curaremimetic neurotoxin binding to nAChR, is sensitive to the duration of exposure to agonist. The concentration of carbachol necessary to prevent one-half of toxin binding over a 30 min incubation with nAChR (K/sub 30/) is 10 ..mu..M when toxin and carbachol are simultaneously added to membrane-bound nAChR, and 3 ..mu..M when nAChR are pretreated with carbachol for 30 min prior to the addition of toxin. These alterations in agonist affinity may be mimicked by modification of nAChR thiol groups. Affinity of nAChR for carbachol is decreased following treatment with dithiothreitol (DTT). Dithio-bis-nitrobenzoic acid treatment of DTT-reduced membranes yields K/sub 30/ values of 5 ..mu..M for carbachol, while N-ethylmaleimide treatment of DTT-reduced nAChR produces nAChR with reduced affinity for carbachol, reflected to K/sub 30/ values of about 400 ..mu..M. In the absence of Ca/sup + +/, K/sub 30/ values for carbachol binding to native and DTT-reduced nAChR are diminished 3 to 6 fold. These affinity alterations are not observed with d-tubocurarine (antagonist) binding to nAChR. Thus, Ca/sup + +/ and the oxidation state of nAChR thiols appear to affect the affinity of nAChR for agonists (but not antagonists), and may therefore be related to agonist-mediated events in receptor activation and/or desensitization.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 5297121
• Journal Information: Life Sci.; (United States), Journal Name: Life Sci.; (United States) Vol. 24:20; ISSN LIFSA
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
560301* -- Chemicals Metabolism & Toxicology-- Cells-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMAL CELLS
ATOMIC IONS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOLOGICAL FUNCTIONS
CALCIUM IONS
CHARGED PARTICLES
DOSE-RESPONSE RELATIONSHIPS
IONS
KINETICS
NERVE CELLS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
REACTION KINETICS
RECEPTORS
RESPONSE MODIFYING FACTORS
SOMATIC CELLS
THIOLS