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Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking
Conversion of vitamin B(12) (cobalamin, Cbl) into the cofactor forms methyl-Cbl (MeCbl) and adenosyl-Cbl (AdoCbl) is required for the function of two crucial enzymes, mitochondrial methylmalonyl-CoA mutase and cytosolic methionine synthase, respectively. The intracellular proteins MMACHC and MMADHC...
Autores principales: | , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Society for Biochemistry and Molecular Biology
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4705923/ https://www.ncbi.nlm.nih.gov/pubmed/26483544 http://dx.doi.org/10.1074/jbc.M115.683268 |
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author | Froese, D. Sean Kopec, Jolanta Fitzpatrick, Fiona Schuller, Marion McCorvie, Thomas J. Chalk, Rod Plessl, Tanja Fettelschoss, Victoria Fowler, Brian Baumgartner, Matthias R. Yue, Wyatt W. |
author_facet | Froese, D. Sean Kopec, Jolanta Fitzpatrick, Fiona Schuller, Marion McCorvie, Thomas J. Chalk, Rod Plessl, Tanja Fettelschoss, Victoria Fowler, Brian Baumgartner, Matthias R. Yue, Wyatt W. |
author_sort | Froese, D. Sean |
collection | PubMed |
description | Conversion of vitamin B(12) (cobalamin, Cbl) into the cofactor forms methyl-Cbl (MeCbl) and adenosyl-Cbl (AdoCbl) is required for the function of two crucial enzymes, mitochondrial methylmalonyl-CoA mutase and cytosolic methionine synthase, respectively. The intracellular proteins MMACHC and MMADHC play important roles in processing and targeting the Cbl cofactor to its destination enzymes, and recent evidence suggests that they may interact while performing these essential trafficking functions. To better understand the molecular basis of this interaction, we have mapped the crucial protein regions required, indicate that Cbl is likely processed by MMACHC prior to interaction with MMADHC, and identify patient mutations on both proteins that interfere with complex formation, via different mechanisms. We further report the crystal structure of the MMADHC C-terminal region at 2.2 Å resolution, revealing a modified nitroreductase fold with surprising homology to MMACHC despite their poor sequence conservation. Because MMADHC demonstrates no known enzymatic activity, we propose it as the first protein known to repurpose the nitroreductase fold solely for protein-protein interaction. Using small angle x-ray scattering, we reveal the MMACHC-MMADHC complex as a 1:1 heterodimer and provide a structural model of this interaction, where the interaction region overlaps with the MMACHC-Cbl binding site. Together, our findings provide novel structural evidence and mechanistic insight into an essential biological process, whereby an intracellular “trafficking chaperone” highly specific for a trace element cofactor functions via protein-protein interaction, which is disrupted by inherited disease mutations. |
format | Online Article Text |
id | pubmed-4705923 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | American Society for Biochemistry and Molecular Biology |
record_format | MEDLINE/PubMed |
spelling | pubmed-47059232016-01-11 Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking Froese, D. Sean Kopec, Jolanta Fitzpatrick, Fiona Schuller, Marion McCorvie, Thomas J. Chalk, Rod Plessl, Tanja Fettelschoss, Victoria Fowler, Brian Baumgartner, Matthias R. Yue, Wyatt W. J Biol Chem Protein Structure and Folding Conversion of vitamin B(12) (cobalamin, Cbl) into the cofactor forms methyl-Cbl (MeCbl) and adenosyl-Cbl (AdoCbl) is required for the function of two crucial enzymes, mitochondrial methylmalonyl-CoA mutase and cytosolic methionine synthase, respectively. The intracellular proteins MMACHC and MMADHC play important roles in processing and targeting the Cbl cofactor to its destination enzymes, and recent evidence suggests that they may interact while performing these essential trafficking functions. To better understand the molecular basis of this interaction, we have mapped the crucial protein regions required, indicate that Cbl is likely processed by MMACHC prior to interaction with MMADHC, and identify patient mutations on both proteins that interfere with complex formation, via different mechanisms. We further report the crystal structure of the MMADHC C-terminal region at 2.2 Å resolution, revealing a modified nitroreductase fold with surprising homology to MMACHC despite their poor sequence conservation. Because MMADHC demonstrates no known enzymatic activity, we propose it as the first protein known to repurpose the nitroreductase fold solely for protein-protein interaction. Using small angle x-ray scattering, we reveal the MMACHC-MMADHC complex as a 1:1 heterodimer and provide a structural model of this interaction, where the interaction region overlaps with the MMACHC-Cbl binding site. Together, our findings provide novel structural evidence and mechanistic insight into an essential biological process, whereby an intracellular “trafficking chaperone” highly specific for a trace element cofactor functions via protein-protein interaction, which is disrupted by inherited disease mutations. American Society for Biochemistry and Molecular Biology 2015-12-04 2015-10-19 /pmc/articles/PMC4705923/ /pubmed/26483544 http://dx.doi.org/10.1074/jbc.M115.683268 Text en © 2015 by The American Society for Biochemistry and Molecular Biology, Inc. Author's Choice—Final version free via Creative Commons CC-BY license (http://creativecommons.org/licenses/by/4.0) . |
spellingShingle | Protein Structure and Folding Froese, D. Sean Kopec, Jolanta Fitzpatrick, Fiona Schuller, Marion McCorvie, Thomas J. Chalk, Rod Plessl, Tanja Fettelschoss, Victoria Fowler, Brian Baumgartner, Matthias R. Yue, Wyatt W. Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking |
title | Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking |
title_full | Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking |
title_fullStr | Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking |
title_full_unstemmed | Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking |
title_short | Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B(12) Trafficking |
title_sort | structural insights into the mmachc-mmadhc protein complex involved in vitamin b(12) trafficking |
topic | Protein Structure and Folding |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4705923/ https://www.ncbi.nlm.nih.gov/pubmed/26483544 http://dx.doi.org/10.1074/jbc.M115.683268 |
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