Interactions between alpha-conotoxin MI and the Torpedo marmorata receptor alpha-delta interface.
The muscle-type nicotinic receptor has two distinguishable acetylcholine binding sites at the alpha-gamma and alpha-delta subunit interfaces; alpha-conotoxins can bind them selectively. Moreover, we previously reported that alpha-conotoxin MI can interact with Torpedo californica and Torpedo marmorata receptors showing that conotoxins can also detect receptors from different species of the same genus [L. Cortez, S.G. del Canto, F. Testai, M.B. de Jiménez Bonino, Conotoxin MI inhibits the acetylcholine binding site of the Torpedo marmorata receptor, Biochem. Biophys. Res. Commun. 295 (2002) 791-795]. Herein, to identify T. marmorata receptor regions involved in alpha-conotoxin MI binding, a photoactivatable reagent was used and labeled sites were mapped by enzymatic proteolysis, MALDI-TOF-MS and Edman degradation. alpha-Conotoxin MI binding determinants were found and studies revealed a second binding motif at the alpha/delta interface. A proposal for receptor-toxin interaction is discussed based on experimental results and docking studies.
Cortez
Leonardo
L
Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires Instituto de Química y Fisicoquímica Biológicas (UBA, CONICET), Junín 956 (1113), Buenos Aires, Argentina.
Marino-Buslje
Cristina
C
de Jiménez Bonino
Mirtha Biscoglio
MB
Hellman
Ulf
U
D000345:Affinity Labels; D000818:Animals; D001665:Binding Sites; D020916:Conotoxins / Q000633:toxicity*; D008024:Ligands; D010449:Peptide Mapping; D021122:Protein Subunits / Q000737:chemistry / Q000302:isolation & purification; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic / Q000737:chemistry / Q000187:drug effects / Q000302:isolation & purification / Q000502:physiology*; D014101:Torpedo
D000345:Affinity Labels; D020916:Conotoxins; D008024:Ligands; D021122:Protein Subunits; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; C036155:conotoxin MI