X-ray crystal structure of TmpA, 2-trimethylaminoethylphosphonate hydroxylase, with Fe, 2OG, and 2-trimethylaminoethylphosphonate

Experimental Data Snapshot

  • Resolution: 1.70 Å
  • R-Value Free: 0.220 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.201 

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A New Microbial Pathway for Organophosphonate Degradation Catalyzed by Two Previously Misannotated Non-Heme-Iron Oxygenases.

Rajakovich, L.J.Pandelia, M.E.Mitchell, A.J.Chang, W.C.Zhang, B.Boal, A.K.Krebs, C.Bollinger Jr., J.M.

(2019) Biochemistry 58: 1627-1647

  • DOI: https://doi.org/10.1021/acs.biochem.9b00044
  • Primary Citation of Related Structures:  
    6NPA, 6NPB, 6NPC, 6NPD

  • PubMed Abstract: 

    The assignment of biochemical functions to hypothetical proteins is challenged by functional diversification within many protein structural superfamilies. This diversification, which is particularly common for metalloenzymes, renders functional annotations that are founded solely on sequence and domain similarities unreliable and often erroneous. Definitive biochemical characterization to delineate functional subgroups within these superfamilies will aid in improving bioinformatic approaches for functional annotation. We describe here the structural and functional characterization of two non-heme-iron oxygenases, TmpA and TmpB, which are encoded by a genomically clustered pair of genes found in more than 350 species of bacteria. TmpA and TmpB are functional homologues of a pair of enzymes (PhnY and PhnZ) that degrade 2-aminoethylphosphonate but instead act on its naturally occurring, quaternary ammonium analogue, 2-(trimethylammonio)ethylphosphonate (TMAEP). TmpA, an iron(II)- and 2-(oxo)glutarate-dependent oxygenase misannotated as a γ-butyrobetaine (γbb) hydroxylase, shows no activity toward γbb but efficiently hydroxylates TMAEP. The product, ( R)-1-hydroxy-2-(trimethylammonio)ethylphosphonate [( R)-OH-TMAEP], then serves as the substrate for the second enzyme, TmpB. By contrast to its purported phosphohydrolytic activity, TmpB is an HD-domain oxygenase that uses a mixed-valent diiron cofactor to enact oxidative cleavage of the C-P bond of its substrate, yielding glycine betaine and phosphate. The high specificities of TmpA and TmpB for their N-trimethylated substrates suggest that they have evolved specifically to degrade TMAEP, which was not previously known to be subject to microbial catabolism. This study thus adds to the growing list of known pathways through which microbes break down organophosphonates to harvest phosphorus, carbon, and nitrogen in nutrient-limited niches.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
TmpA, 2-trimethylaminoethylphosphonate hydroxylase
A, B
383Leisingera caeruleaMutation(s): 0 
EC: 1
Find proteins for A0A4V8H042 (Leisingera caerulea)
Explore A0A4V8H042 
Go to UniProtKB:  A0A4V8H042
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA0A4V8H042
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.70 Å
  • R-Value Free: 0.220 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.201 
  • Space Group: P 41 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 86.901α = 90
b = 86.901β = 90
c = 220.613γ = 90
Software Package:
Software NamePurpose
HKL-2000data scaling
PDB_EXTRACTdata extraction
HKL-2000data reduction

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Science Foundation (NSF, United States)United StatesMCB-1330784

Revision History  (Full details and data files)

  • Version 1.0: 2019-03-06
    Type: Initial release
  • Version 1.1: 2019-04-10
    Changes: Author supporting evidence, Data collection, Database references
  • Version 1.2: 2019-11-27
    Changes: Author supporting evidence
  • Version 1.3: 2023-10-11
    Changes: Data collection, Database references, Derived calculations, Refinement description