2NTK

Crystal structure of PurO/IMP from Methanothermobacter thermoautotrophicus


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.03 Å
  • R-Value Free: 0.245 
  • R-Value Work: 0.218 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

A novel function for the N-terminal nucleophile hydrolase fold demonstrated by the structure of an archaeal inosine monophosphate cyclohydrolase.

Kang, Y.N.Tran, A.White, R.H.Ealick, S.E.

(2007) Biochemistry 46: 5050-5062

  • DOI: 10.1021/bi061637j
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • Inosine 5'-monophosphate (IMP) cyclohydrolase catalyzes the cyclization of 5-formaminoimidazole-4-carboxamide ribonucleotide (FAICAR) to IMP in the final step of de novo purine biosynthesis. Two major types of this enzyme have been discovered to date ...

    Inosine 5'-monophosphate (IMP) cyclohydrolase catalyzes the cyclization of 5-formaminoimidazole-4-carboxamide ribonucleotide (FAICAR) to IMP in the final step of de novo purine biosynthesis. Two major types of this enzyme have been discovered to date: PurH in Bacteria and Eukarya and PurO in Archaea. The structure of the MTH1020 gene product from Methanothermobacter thermoautotrophicus was previously solved without functional annotation but shows high amino acid sequence similarity to other PurOs. We determined the crystal structure of the MTH1020 gene product in complex with either IMP or 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) at 2.0 and 2.6 A resolution, respectively. On the basis of the sequence analysis, ligand-bound structures, and biochemical data, MTH1020 is confirmed as an archaeal IMP cyclohydrolase, thus designated as MthPurO. MthPurO has a four-layered alphabeta betaalpha core structure, showing an N-terminal nucleophile (NTN) hydrolase fold. The active site is located at the deep pocket between two central beta-sheets and contains residues strictly conserved within PurOs. Comparisons of the two types of IMP cyclohydrolase, PurO and PurH, revealed that there are no similarities in sequence, structure, or the active site architecture, suggesting that they are evolutionarily not related to each other. The MjR31K mutant of PurO from Methanocaldococcus jannaschii showed 76% decreased activity and the MjE102Q mutation completely abolished enzymatic activity, suggesting that these highly conserved residues play critical roles in catalysis. Interestingly, green fluorescent protein (GFP), which has no structural homology to either PurO or PurH but catalyzes a similar intramolecular cyclohydrolase reaction required for chromophore maturation, utilizes Arg96 and Glu222 in a mechanism analogous to that of PurO.


    Organizational Affiliation

    Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
IMP cyclohydrolase
A, B, C, D
222Methanothermobacter thermautotrophicus (strain ATCC 29096 / DSM 1053 / JCM 10044 / NBRC 100330 / Delta H)Mutation(s): 0 
Gene Names: purO
EC: 3.5.4.10
Find proteins for O27099 (Methanothermobacter thermautotrophicus (strain ATCC 29096 / DSM 1053 / JCM 10044 / NBRC 100330 / Delta H))
Go to UniProtKB:  O27099
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
IMP
Query on IMP

Download SDF File 
Download CCD File 
A, B, C, D
INOSINIC ACID
C10 H13 N4 O8 P
GRSZFWQUAKGDAV-KQYNXXCUSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.03 Å
  • R-Value Free: 0.245 
  • R-Value Work: 0.218 
  • Space Group: P 32
Unit Cell:
Length (Å)Angle (°)
a = 85.975α = 90.00
b = 85.975β = 90.00
c = 124.442γ = 120.00
Software Package:
Software NamePurpose
ADSCdata collection
CNSphasing
CNSrefinement
HKL-2000data scaling
HKL-2000data reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2007-04-24
    Type: Initial release
  • Version 1.1: 2008-05-01
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance