MeaB, A Bacterial Homolog of MMAA, in the Nucleotide Free Form

Experimental Data Snapshot

  • Resolution: 1.70 Å
  • R-Value Free: 0.208 
  • R-Value Work: 0.175 
  • R-Value Observed: 0.177 

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Crystal structure and mutagenesis of the metallochaperone MeaB: insight into the causes of methylmalonic aciduria.

Hubbard, P.A.Padovani, D.Labunska, T.Mahlstedt, S.A.Banerjee, R.Drennan, C.L.

(2007) J Biol Chem 282: 31308-31316

  • DOI: https://doi.org/10.1074/jbc.M704850200
  • Primary Citation of Related Structures:  
    2QM7, 2QM8

  • PubMed Abstract: 

    MeaB is an auxiliary protein that plays a crucial role in the protection and assembly of the B(12)-dependent enzyme methylmalonyl-CoA mutase. Impairments in the human homologue of MeaB, MMAA, lead to methylmalonic aciduria, an inborn error of metabolism. To explore the role of this metallochaperone, its structure was solved in the nucleotide-free form, as well as in the presence of product, GDP. MeaB is a homodimer, with each subunit containing a central alpha/beta-core G domain that is typical of the GTPase family, as well as alpha-helical extensions at the N and C termini that are not found in other metalloenzyme chaperone GTPases. The C-terminal extension appears to be essential for nucleotide-independent dimerization, and the N-terminal region is implicated in protein-protein interaction with its partner protein, methylmalonyl-CoA mutase. The structure of MeaB confirms that it is a member of the G3E family of P-loop GTPases, which contains other putative metallochaperones HypB, CooC, and UreG. Interestingly, the so-called switch regions, responsible for signal transduction following GTP hydrolysis, are found at the dimer interface of MeaB instead of being positioned at the surface of the protein where its partner protein methylmalonyl-CoA mutase should bind. This observation suggests a large conformation change of MeaB must occur between the GDP- and GTP-bound forms of this protein. Because of their high sequence homology, the missense mutations in MMAA that result in methylmalonic aciduria have been mapped onto MeaB and, in conjunction with mutagenesis data, provide possible explanations for the pathology of this disease.

  • Organizational Affiliation

    Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
337Methylorubrum extorquens AM1Mutation(s): 3 
Gene Names: meaB
Find proteins for Q8RPA0 (Methylorubrum extorquens)
Explore Q8RPA0 
Go to UniProtKB:  Q8RPA0
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8RPA0
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.70 Å
  • R-Value Free: 0.208 
  • R-Value Work: 0.175 
  • R-Value Observed: 0.177 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 59.41α = 90
b = 77.04β = 95.55
c = 79.95γ = 90
Software Package:
Software NamePurpose
ADSCdata collection
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-08-28
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Source and taxonomy, Version format compliance
  • Version 1.2: 2021-10-20
    Changes: Database references, Derived calculations