A motif present in the main cytoplasmic loop of nicotinic acetylcholine receptors and catalases

A motif containing five conserved amino acids (RXPXTH (X)(14)P) was detecte d in 111 proteins, including 82 nicotinic acetylcholine receptor (nAChR) su bunits and 20 catalases. To explore possible functional roles of this motif in nAChRs two approaches were used: first, the motif sequences in nAChR su bunits and catalases were analysed and compared, and, second, deletions in the rat alpha2 and beta4 nAChR subunits expressed in Xenopus oocytes were a nalysed. Compared to the three-dimensional structure of bovine hepatic cata lase, structural coincidences were found in the motif of catalases and nACh Rs. On the other hand, partial deletions of the motif in the alpha2 or beta 4 subunits and injection of the mutants into oocytes was followed by a very weak expression of functional nAChRs; oocytes injected with alpha2 and bet a4 subunits in which the entire motif had been deleted failed to elicit any acetylcholine currents. The results suggest that the motif may play a role in the activation of nAChRs.