Crystal structure of the siroheme decarboxylase NirDL

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.271 
  • R-Value Work: 0.225 
  • R-Value Observed: 0.228 

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The Crystal Structure of Siroheme Decarboxylase in Complex with Iron-Uroporphyrin III Reveals Two Essential Histidine Residues

Haufschildt, K.Schmelz, S.Kriegler, T.M.Neumann, A.Streif, J.Arai, H.Heinz, D.W.Layer, G.

(2014) J Mol Biol 426: 3272

  • DOI: https://doi.org/10.1016/j.jmb.2014.07.021
  • Primary Citation of Related Structures:  
    4CH7, 4CZC

  • PubMed Abstract: 

    The isobacteriochlorin heme d1 serves as an essential cofactor in the cytochrome cd1 nitrite reductase NirS that plays an important role for denitrification. During the biosynthesis of heme d1, the enzyme siroheme decarboxylase catalyzes the conversion of siroheme to 12,18-didecarboxysiroheme. This enzyme was discovered recently (Bali S, Lawrence AD, Lobo SA, Saraiva LM, Golding BT, Palmer DJ et al. Molecular hijacking of siroheme for the synthesis of heme and d1 heme. Proc Natl Acad Sci USA 2011;108:18260-5) and is only scarcely characterized. Here, we present the crystal structure of the siroheme decarboxylase from Hydrogenobacter thermophilus representing the first three-dimensional structure for this type of enzyme. The overall structure strikingly resembles those of transcriptional regulators of the Lrp/AsnC family. Moreover, the structure of the enzyme in complex with a substrate analog reveals first insights into its active-site architecture. Through site-directed mutagenesis and subsequent biochemical characterization of the enzyme variants, two conserved histidine residues within the active site are identified to be involved in substrate binding and catalysis. Based on our results, we propose a potential catalytic mechanism for the enzymatic reaction catalyzed by the siroheme decarboxylase.

  • Organizational Affiliation

    Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
NIRD-LIKE PROTEIN342Hydrogenobacter thermophilus TK-6Mutation(s): 0 
Find proteins for D3DFS4 (Hydrogenobacter thermophilus (strain DSM 6534 / IAM 12695 / TK-6))
Explore D3DFS4 
Go to UniProtKB:  D3DFS4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupD3DFS4
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on MSE
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.271 
  • R-Value Work: 0.225 
  • R-Value Observed: 0.228 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 101.35α = 90
b = 72.09β = 100.4
c = 51.2γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2014-07-30
    Type: Initial release
  • Version 1.1: 2014-08-13
    Changes: Database references
  • Version 1.2: 2014-09-10
    Changes: Database references