1LI4

Human S-adenosylhomocysteine hydrolase complexed with neplanocin


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.01 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.197 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Catalytic strategy of S-adenosyl-L-homocysteine hydrolase: Transition-state stabilization and the avoidance of abortive reactions

Yang, X.Hu, Y.Yin, D.H.Turner, M.A.Wang, M.Borchardt, R.T.Howell, P.L.Kuczera, K.Schowen, R.L.

(2003) Biochemistry 42: 1900-1909

  • DOI: 10.1021/bi0262350

  • PubMed Abstract: 
  • S-Adenosylhomocysteine hydrolase (AdoHcy hydrolase) crystallizes from solutions containing the intermediate analogue neplanocin A with the analogue bound in its 3'-keto form at the active sites of all of its four subunits and the four tightly bound c ...

    S-Adenosylhomocysteine hydrolase (AdoHcy hydrolase) crystallizes from solutions containing the intermediate analogue neplanocin A with the analogue bound in its 3'-keto form at the active sites of all of its four subunits and the four tightly bound cofactors in their reduced (NADH) state. The enzyme is in the closed conformation, which corresponds to the structure in which the catalytic chemistry occurs. Examination of the structure in the light of available, very detailed kinetic studies [Porter, D. J., Boyd, F. L. (1991) J. Biol. Chem. 266, 21616-21625. Porter, D. J., Boyd, F. L. (1992) J. Biol. Chem. 267, 3205-3213. Porter, D. J. (1998) J. Biol. Chem. 268, 66-73] suggests elements of the catalytic strategy of AdoHcy hydrolase for acceleration of the reversible conversion of AdoHcy to adenosine (Ado) and homocysteine (Hcy). The enzyme, each subunit of which possesses a substrate-binding domain that in the absence of substrate is in rapid motion relative to the tetrameric core of the enzyme, first binds substrate and ceases motion. Probably concurrently with oxidation of the substrate to its 3'-keto form, the closed active site is "sealed off" from the environment, as indicated by a large (10(8)(-)(9)-fold) reduction in the rate of departure of ligands, a feature that prevents exposure of the labile 3'-keto intermediates to the aqueous environment. Elimination of the 5'-substituent (Hcy in the hydrolytic direction, water in the synthetic direction) generates the central intermediate 4',5'-didehydro-5'-deoxy-3'-ketoadenosine. Abortive 3'-reduction of the central intermediate is prevented by a temporary suspension of all or part of the redox catalytic power of the enzyme during the existence of the central intermediate. The abortive reduction is 10(4)-fold slower than the productive reductions at the ends of the catalytic cycle and has a rate constant similar to those of nonenzymic intramolecular model reactions. The mechanism for suspending the redox catalytic power appears to be a conformationally induced increase in the distance across which hydride transfer must occur between cofactor and substrate, the responsible conformational change again being that which "seals" the active site. The crystal structure reveals a well-defined chain of three water molecules leading from the active site to the subunit surface, which may serve as a relay for proton exchange between solvent and active site in the closed form of the enzyme, permitting maintenance of active-site functional groups in catalytically suitable protonation states.


    Organizational Affiliation

    Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, Kansas 66047, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
S-adenosylhomocysteine hydrolase
A
432Homo sapiensMutation(s): 0 
Gene Names: AHCY (SAHH)
EC: 3.3.1.1
Find proteins for P23526 (Homo sapiens)
Go to Gene View: AHCY
Go to UniProtKB:  P23526
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NAD
Query on NAD

Download SDF File 
Download CCD File 
A
NICOTINAMIDE-ADENINE-DINUCLEOTIDE
C21 H27 N7 O14 P2
BAWFJGJZGIEFAR-NNYOXOHSSA-N
 Ligand Interaction
NOC
Query on NOC

Download SDF File 
Download CCD File 
A
3-(6-AMINO-PURIN-9-YL)-5-HYDROXYMETHYL-CYCLOPENTANE-1,2-DIOL
NEPLANOCIN
C11 H15 N5 O3
UGRNVLGKAGREKS-FAYXRDSDSA-N
 Ligand Interaction
IPA
Query on IPA

Download SDF File 
Download CCD File 
A
ISOPROPYL ALCOHOL
2-PROPANOL
C3 H8 O
KFZMGEQAYNKOFK-UHFFFAOYSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
7CYKi: 110 nM (100) BINDINGDB
7CYIC50: 303 - 4850 nM (100) BINDINGDB
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.01 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.197 
  • Space Group: F 2 2 2
Unit Cell:
Length (Å)Angle (°)
a = 92.830α = 90.00
b = 135.670β = 90.00
c = 171.490γ = 90.00
Software Package:
Software NamePurpose
CNSrefinement
DENZOdata reduction
SCALEPACKdata scaling
CNSphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-05-20
    Type: Initial release
  • Version 1.1: 2008-04-28
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance