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-Structure paper
タイトル | Structural insight into G-protein chaperone-mediated maturation of a bacterial adenosylcobalamin-dependent mutase. |
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ジャーナル・号・ページ | J Biol Chem, Vol. 299, Issue 9, Page 105109, Year 2023 |
掲載日 | 2023年7月28日 |
著者 | Francesca A Vaccaro / Daphne A Faber / Gisele A Andree / David A Born / Gyunghoon Kang / Dallas R Fonseca / Marco Jost / Catherine L Drennan / |
PubMed 要旨 | G-protein metallochaperones are essential for the proper maturation of numerous metalloenzymes. The G-protein chaperone MMAA in humans (MeaB in bacteria) uses GTP hydrolysis to facilitate the ...G-protein metallochaperones are essential for the proper maturation of numerous metalloenzymes. The G-protein chaperone MMAA in humans (MeaB in bacteria) uses GTP hydrolysis to facilitate the delivery of adenosylcobalamin (AdoCbl) to AdoCbl-dependent methylmalonyl-CoA mutase, an essential metabolic enzyme. This G-protein chaperone also facilitates the removal of damaged cobalamin (Cbl) for repair. Although most chaperones are standalone proteins, isobutyryl-CoA mutase fused (IcmF) has a G-protein domain covalently attached to its target mutase. We previously showed that dimeric MeaB undergoes a 180° rotation to reach a state capable of GTP hydrolysis (an active G-protein state), in which so-called switch III residues of one protomer contact the G-nucleotide of the other protomer. However, it was unclear whether other G-protein chaperones also adopted this conformation. Here, we show that the G-protein domain in a fused system forms a similar active conformation, requiring IcmF oligomerization. IcmF oligomerizes both upon Cbl damage and in the presence of the nonhydrolyzable GTP analog, guanosine-5'-[(β,γ)-methyleno]triphosphate, forming supramolecular complexes observable by mass photometry and EM. Cryo-EM structural analysis reveals that the second protomer of the G-protein intermolecular dimer props open the mutase active site using residues of switch III as a wedge, allowing for AdoCbl insertion or damaged Cbl removal. With the series of structural snapshots now available, we now describe here the molecular basis of G-protein-assisted AdoCbl-dependent mutase maturation, explaining how GTP binding prepares a mutase for cofactor delivery and how GTP hydrolysis allows the mutase to capture the cofactor. |
リンク | J Biol Chem / PubMed:37517695 / PubMed Central |
手法 | EM (単粒子) |
解像度 | 4.6 - 7.3 Å |
構造データ | EMDB-40751, PDB-8ssl: EMDB-40758, PDB-8sta: |
化合物 | ChemComp-GDP: ChemComp-MG: |
由来 |
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キーワード | ISOMERASE / supramolecular complex / b12-binding / g-protein chaperone / mutase |