Mapping the functional topography of a receptor.
Photoactivatable derivatives of the alpha-neurotoxin II from Naja naja oxiana are useful tools for investigating the three dimensional architecture of the extra-membrane part of the nicotinic acetylcholine receptor from the electric tissue of Torpedo californica. Three derivatives, carrying an azidobenzoyl group in position Lys-15, Lys-26, and Lys-46, respectively, are shown to react differently within the receptor's quaternary structure. Especially the Lys-26 and Lys-46 derivatives can be used for differentiating between the two nonequivalent alpha-subunits. The Lys-26 derivative is applied for probing the receptor subunits next to the alpha-subunit: the gamma-subunit is shown to be located next to the alpha-subunit binding d-tubocurarine with high affinity. The delta-subunit is the neighbor of the low affinity alpha-subunit. We radioiodinated the toxin derivatives and localized the 125I at the His-31 residue of the toxin. Very little label was found in position Tyr-24, the only tyrosine residue of the toxin, or in position His-4, the only other histidine residue. This result is important for the cleavage experiments necessary in attempts to identify the receptor sequence which reacted with the photolabel.
Hucho
F
F
Institut für Biochemie, Freien Universität Berlin.
Weise
C
C
Kreienkamp
H J
HJ
Tsetlin
V
V
Utkin
Y
Y
Machold
J
J
D000345:Affinity Labels; D000595:Amino Acid Sequence; D000818:Animals; D002853:Chromatography, Liquid; D003039:Cobra Neurotoxin Proteins / Q000737:chemistry; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D010777:Photochemistry; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000502:physiology; D012911:Snakes; D014101:Torpedo
D000345:Affinity Labels; D003039:Cobra Neurotoxin Proteins; D003432:Cross-Linking Reagents; D011978:Receptors, Nicotinic; C076649:neurotoxin II, Naja naja oxiana