Accession Number : ADP008868

Title :   Structure-Function Relationships in Acetylcholinesterase: Modelling, Mutagenesis and Comparative Studies.

Corporate Author : WEIZMANN INST OF SCIENCE REHOVOT (ISRAEL)

Personal Author(s) : Silman, I. ; Harel, M. ; Eichler, J. ; Krejci, E. ; Anselmet, A.

Report Date : 13 MAY 1993

Pagination or Media Count : 10

Abstract : The high sequence homology of human BChE and Torpedo AChE permitted modeling of the former on the basis of the 3-D structure of the latter. The H-BChE model closely resembles the Torpedo AChE structure in overall features. However, six of the conserved amino acids lining the active-site gorge of AChE are absent in BChE. Modeling showed that two of these residues, Phe288 and Phe290, replaced by Leu and Val, respectively, in BChE, may prevent entrance of BCh to the acyl-binding pocket. Their mutation to Leu and Val in Torpedo AChE produced a double mutant which hydrolysed butyrylthiocholine almost as well as acetylthiocholine. Trp279, at the entrance to the active-site gorge, is absent in BChE. Modeling designated it as part of the peripheral anionic site, which is lacking in BChE. Site-directed mutagenesis to Ala, supported this assignment, since the Trp279Ala mutant displayed greatly reduced inhibition by the peripheral site-specific ligand, propidium. Three peripheral site ligands were less effective on chicken than on Torpedo AChE. Whereas the concentration-dependence of activity towards acetylthiocholine is almost identical for the two, substrate inhibition of chicken AChE is weaker than of Torpedo AChE. Two bisquaternary ligands which are believed to bridge the 'anionic' subsite of the active site and the peripheral site are weaker inhibitors of chicken than of Torpedo AChE, whereas a shorter bisquaternary ligand inhibits both similarly.

Descriptors :   *MUTATIONS, *TORPEDOES, *ACETYLCHOLINESTERASE, ALIGNMENT, ALLOCATIONS, ALUMINUM ARSENIDES, AMINO ACIDS, BRIDGES, CANYONS, CHICKENS, ENZYMES, HUMANS, INHIBITION, INHIBITORS, LIGANDS, LININGS, MODELS, MOUTH, RESIDUES, SEQUENCES, SITES, STRUCTURES, SUBSTRATES.

Subject Categories : Inorganic Chemistry
      Biochemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE