4LC1

MeaB, A Bacterial Homolog of MMAA, Bound to GDP and crystallized in the presence of GDP and [AlF4]-

Summary for 4LC1

• Entry DOI: 10.2210/pdb4lc1/pdb
• Related: 2QM7 2QM8 4JYB 4JYC
• Descriptor: Methylmalonyl-CoA mutase accessory protein, GUANOSINE-5'-DIPHOSPHATE, GLYCEROL, ... (4 entities in total)
• Functional Keywords: alpha and beta protein, metallochaperone, chaperone
• Biological source: Methylobacterium extorquens
• Total number of polymer chains: 2
• Total formula weight: 72173.52

Authors

Koutmos, M.,Padovani, D.,Lofgren, M.,Banerjee, R. (deposition date: 2013-06-21, release date: 2013-09-25, Last modification date: 2023-09-20)

Primary citation

Lofgren, M.,Koutmos, M.,Banerjee, R.
Autoinhibition and Signaling by the Switch II Motif in the G-protein Chaperone of a Radical B12 Enzyme.
J.Biol.Chem., 288:30980-30989, 2013

PubMed Abstract: MeaB is an accessory GTPase protein involved in the assembly, protection, and reactivation of 5'-deoxyadenosyl cobalamin-dependent methylmalonyl-CoA mutase (MCM). Mutations in the human ortholog of MeaB result in methylmalonic aciduria, an inborn error of metabolism. G-proteins typically utilize conserved switch I and II motifs for signaling to effector proteins via conformational changes elicited by nucleotide binding and hydrolysis. Our recent discovery that MeaB utilizes an unusual switch III region for bidirectional signaling with MCM raised questions about the roles of the switch I and II motifs in MeaB. In this study, we addressed the functions of conserved switch II residues by performing alanine-scanning mutagenesis. Our results demonstrate that the GTPase activity of MeaB is autoinhibited by switch II and that this loop is important for coupling nucleotide-sensitive conformational changes in switch III to elicit the multiple chaperone functions of MeaB. Furthermore, we report the structure of MeaB·GDP crystallized in the presence of AlFx(-) to form the putative transition state analog, GDP·AlF4(-). The resulting crystal structure and its comparison with related G-proteins support the conclusion that the catalytic site of MeaB is incomplete in the absence of the GTPase-activating protein MCM and therefore unable to stabilize the transition state analog. Favoring an inactive conformation in the absence of the client MCM protein might represent a strategy for suppressing the intrinsic GTPase activity of MeaB in which the switch II loop plays an important role.

PubMed: 23996001
DOI: 10.1074/jbc.M113.499970

Experimental method

X-RAY DIFFRACTION (1.8 Å)