Sandbox uc 17
From Proteopedia
Two crystal structures of the B1 immunoglobulin-binding domain of streptococcal protein G and comparison with NMR.
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Background
The structure of the 56-residue B1 immunoglobulin-binding domain from streptococcal protein G has been determined in two different crystal forms. The crystal structures were deduced by molecular replacement, based on the structure of the B2 domain (Brookhaven accession code 1PGX). Final R values are 0.174 and 0.198 for orthorhombic and trigonal forms, for diffraction data from 6.0 to 2.07 A and from 6 to 1.92 A, respectively. The orthorhombic crystals have an unusually high packing density for protein crystals, with Vm = 1.66 and a solvent content of 26%. The protein structure is found to be very similar (rms deviation 0.25 A for 56 C alpha's) in the two crystal forms, with an efficiently packed hydrophobic core between a four-stranded beta-sheet and a four-turn alpha-helix. The B1 domain has the same fold and general structure as the B2 domain (rms deviations 0.36 and 0.39 A), despite the six residue differences between them. The crystallographic models differ from NMR-derived models in several local regions, primarily in the loop involving residues 46-51; other significant variations are observed in the helix and in the structure of bound water. The primary crystal contact is the same in both crystal forms, involving both sheet edges to form extended beta-sheets throughout the crystals.
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Results
The X-ray structure of the E2020-TcAChE complex shows that E2020 has a along the active-site gorge, extending from the anionic subsite () of the active site, at the bottom, to the peripheral anionic site (), at the top, via aromatic stacking interactions with conserved aromatic acid residues. E2020 does not, however, interact directly with either the catalytic triad or the 'oxyanion hole' but only .
Conclusions
The X-ray structure shows, a posteriori, that the design of E2020 took advantage of several important features of the active-site gorge of AChE, to produce a drug with both high affinity for AChE and a high degree of selectivity for AChE versus butyrylcholinesterase (BChE). It also delineates voids within the gorge that are not occupied by E2020 and could provide sites for potential modification of E2020 to produce drugs with improved pharmacological profiles.
About this Structure
1EVE is a 1 chain structure with sequence from Torpedo californica. The June 2004 RCSB PDB Molecule of the Month feature on Acetylcholinesterase by David S. Goodsell is 10.2210/rcsb_pdb/mom_2004_6. Full crystallographic information is available from OCA.
Additional Resources
For additional information, see: Alzheimer's Disease
Reference
Structure of acetylcholinesterase complexed with E2020 (Aricept): implications for the design of new anti-Alzheimer drugs., Kryger G, Silman I, Sussman JL, Structure. 1999 Mar 15;7(3):297-307. PMID:10368299
See 1eve (Chinese), 1eve (French), 1eve (Arabic), 1eve (Russian), 1eve (Spanish), & 1eve (Turkish).
