High resolution melting analysis of the MMAA gene in patients with cblA and in those with undiagnosed methylmalonic aciduria

Dempsey-Nunez, Laura; Illson, Margaret L.; Kent, Jana; Huang, Qiuying; Brebner, Alison; Watkins, David; Gilfix, Brian M.; Wittwer, Carl T.; Rosenblatt, David S.

doi:10.1016/j.ymgme.2012.09.012

Cited by 23 publications

(20 citation statements)

References 19 publications

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“…Switch III mutations, G274S and K276E in human MMAA have been reported recently in patients with methylmalonic aciduria 7 . The intrinsic GTPase activity and affinity for nucleotides or for MCM are largely unaffected in the corresponding MeaB mutants (G186S and K188E) as also seen with the alanine mutations in the switch III region (Supplementary Tables 3–5).…”

Section: Resultsmentioning

confidence: 92%

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A switch III motif relays signaling between a B12 enzyme and its G-protein chaperone

et al. 2013

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Fidelity during cofactor assembly is essential for the proper functioning of metalloenzymes and is ensured by specific chaperones. MeaB, a G-protein chaperone for the coenzyme B12-dependent radical enzyme, methylmalonyl-CoA mutase (MCM), utilizes the energy of GTP binding and/or hydrolysis to regulate cofactor loading into MCM, protect MCM from inactivation, and rescue MCM inactivated during turnover. Typically, G-proteins signal to client proteins using the conformationally mobile switch I and II loops. Crystallographic snapshots of MeaB reported herein reveal a novel switch III element, which exhibits substantial conformational plasticity. Using alanine-scanning mutagenesis, we demonstrate that the switch III motif is critical for bidirectional signal transmission of the GTPase activating protein activity of MCM and the chaperone functions of MeaB in the MeaB:MCM complex. Mutations in the switch III loop identified in patients corrupt this inter-protein communication and lead to methylmalonic aciduria, an inborn error of metabolism.

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Section: Resultsmentioning

confidence: 92%

“…The bacterial protein MeaB 4 and its human ortholog MMAA 5 are chaperones that regulate docking of coenzyme B 12 (5′-deoxyadenosylcobalamin or AdoCbl) into the radical enzyme methylmalonyl-CoA mutase (MCM) 6,7 . MCM uses AdoCbl to catalyze the chemically challenging 1,2-rearrangement of ( R )-methylmalonyl-CoA to succinyl-CoA 8 .…”

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confidence: 99%

A switch III motif relays signaling between a B12 enzyme and its G-protein chaperone

et al. 2013

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“…2c). A mutation in CblA corresponding to the Lys-188 residue in MeaB is pathogenic (49). We have shown that mutation of Lys-188 has pleiotropic consequences including loss of regulated GTPase-dependent AdoCbl loading into MCM and impaired repair of inactive MCM.…”

Section: Discussionmentioning

confidence: 98%

Autoinhibition and Signaling by the Switch II Motif in the G-protein Chaperone of a Radical B12 Enzyme

Lofgren

Koutmos

Banerjee

2013

Journal of Biological Chemistry

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Background: MeaB is a G-protein chaperone of methylmalonyl-CoA mutase (MCM). Results: Mutations in the canonical switch II motif disrupt signaling in the MeaB-MCM complex. Conclusion:The switch II loop is autoinhibitory for the intrinsic GTPase activity of MeaB. Significance: Signaling in the MeaB-MCM complex is achieved via nucleotide-dependent conformational coupling between switches II and III.

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“…If untreated, metabolic crisis can result in lethal multi-organ failure, underlining the importance of improving the knowledge about disease pathology (Hörster et al, 2007;Matsui, Mahoney, & Rosenberg, 1983). To date, about 140 cblA patients harboring 41 different mutations in MMAA have been published (Ampola, Mahoney, Nakamura, & Tanaka, 1975;Dempsey-Nunez et al, 2012;Dobson et al, 2002b;Gravel, Mahoney, Ruddle, and Rosenberg, 1975;Hörster et al, 2007;Lerner-Ellis et al, 2004;Martínez et al, 2005;Matsui et al, 1983;Merinero et al, 2008;Nizon et al, 2013;Rosenberg, Lilljeqvist, and Hsia, 1968;Vatanavicharn et al, 2012;Yang et al, 2004). The nonsense mutation c.433C>T (p.Arg145*), resulting in a premature stop-codon, accounts for the majority of pathogenic alleles (Lerner-Ellis et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Protein destabilization and loss of protein‐protein interaction are fundamental mechanisms in cblA ‐type methylmalonic aciduria

et al. 2017

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Mutations in the human MMAA gene cause the metabolic disorder cblA-type methylmalonic aciduria (MMA), although knowledge of the mechanism of dysfunction remains lacking. MMAA regulates the incorporation of the cofactor adenosylcobalamin (AdoCbl), generated from the MMAB adenosyltransferase, into the destination enzyme methylmalonyl-CoA mutase (MUT). This function of MMAA depends on its GTPase activity, which is stimulated by an interaction with MUT. Here, we present 67 new patients with cblA-type MMA, identifying 19 novel mutations. We biochemically investigated how missense mutations in MMAA in 22 patients lead to disease. About a third confer instability to the recombinant protein in bacterial and human expression systems. All 15 purified mutant proteins demonstrated wild-type like intrinsic GTPase activity and only one (p.Asp292Val), where the mutation is in the GTP binding domain, revealed decreased GTP binding. However, all mutations strongly decreased functional association with MUT by reducing GTPase activity stimulation upon incubation with MUT, while nine mutant proteins additionally lost the ability to physically bind MUT. Finally, all mutations interfered with gating the transfer of AdoCbl from MMAB to MUT. This work suggests loss of functional interaction between MMAA and MUT as a disease-causing mechanism that impacts processing and assembly of a cofactor to its destination enzyme.

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High resolution melting analysis of the MMAA gene in patients with cblA and in those with undiagnosed methylmalonic aciduria

Cited by 23 publications

References 19 publications

A switch III motif relays signaling between a B12 enzyme and its G-protein chaperone

A switch III motif relays signaling between a B12 enzyme and its G-protein chaperone

Autoinhibition and Signaling by the Switch II Motif in the G-protein Chaperone of a Radical B12 Enzyme

Protein destabilization and loss of protein‐protein interaction are fundamental mechanisms in cblA ‐type methylmalonic aciduria

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