2QM7: Meab, A Bacterial Homolog Of Mmaa, Bound To Gdp

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.
PDB ID: 2QM7Download
MMDB ID: 59502
PDB Deposition Date: 2007/7/14
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.85  Å
Source Organism:
Similar Structures:
Biological Unit for 2QM7: dimeric; determined by author and by software (PISA)
Molecular Components in 2QM7
Label Count Molecule
Proteins (2 molecules)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB