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Insights into substrate and product traffic in the Drosophila melanogaster acetylcholinesterase active site gorge by enlarging a back channel
Author(s) -
Nachon Florian,
Stojan Jure,
Fournier Didier
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06413.x
Subject(s) - drosophila melanogaster , acetylcholinesterase , channel (broadcasting) , substrate (aquarium) , active site , engineering , electrical engineering , biology , ecology , enzyme , biochemistry , gene
To test a product exit differing from the substrate entrance in the active site of acetylcholinesterase (EC 3.1.1.7), we enlarged a channel located at the bottom of the active site gorge in the Drosophila enzyme. Mutation of Trp83 to Ala or Glu widens the channel from 5 Å to 9 Å. The kinetics of substrate hydrolysis and the effect of ligands that close the main entrance suggest that the mutations facilitate both product exit and substrate entrance. Thus, in the wild‐type, the channel is so narrow that the ‘back door’ is used by at most 5% of the traffic, with the majority of traffic passing through the main entrance. In mutants Trp83Ala and Trp83Glu, ligands that close the main entrance do not inhibit substrate hydrolysis because the traffic can pass via an alternative route, presumably the enlarged back channel.