Regulation of eukaryotic acetyl-CoA carboxylases

Hagmann, Anna. Regulation of eukaryotic acetyl-CoA carboxylases. 2018, Doctoral Thesis, University of Basel, Faculty of Science.


Official URL: http://edoc.unibas.ch/diss/DissB_12721

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Many biological carboxylation reactions are catalyzed by ubiquitous biotin-dependent carboxylases. Their mechanism involves three conserved functional components; First, a biotin moiety, covalently linked to the biotin carboxyl carrier protein (BCCP) is carboxylated under ATP consumption at the biotin carboxylase (BC). Then the BCCP translocates to the CT active site where the carboxyl group is transferred to the substrate. Most prokaryotic biotin-dependent carboxylases are multi-subunit complexes, with functional components distributed over multiple protein subunits. The eukaryotic acetyl-CoA carboxylases (ACCs), however, are multienzymes, which combine all functional components as domains into one polypeptide chain, which further dimerizes. They catalyze the committed step in fatty-acid biosynthesis: the carboxylation of acetyl-CoA to malonyl-CoA. ACCs are highly regulated and their activity has been linked to diseases such as cancer and the metabolic syndrome. Mechanisms of ACC regulation involve allostery, phosphorylation and filament formation. The aim of this thesis is to reveal the architecture of biotin-dependent carboxylase multienzymes and the structural basis for the regulation of eukaryotic ACCs.
Chapter two reveals the dynamic organization of a prokaryotic biotin-dependent carboxylase multienzyme, the hexameric long-chain acyl-CoA carboxylase YCC of Deinococcus radiodurans, based on crystallographic structure determination of isolated domains, negative stain electron microscopy (EM) and small-angle X-ray scattering (SAXS).
In chapter three, the architecture of fungal ACCs is elucidated by crystal structures of different fragments of the enzyme in combination with negative stain EM and SAXS. Fungal ACC regulation is mediated by a phosphorylated loop, which wedges into the non-catalytic central domain (CD), restricting ACC to a catalytically non-competent conformation.
Using cryo-EM, in chapter four, the architecture of the activated human ACC filament (ACCCit) and a thus far unknown, inhibited ACC filament type, which forms upon binding of BRCT domains of BRCA1 (ACCBRCT) is revealed. Interactions between protomers of both filaments are mediated by the non-catalytic CD and provide the basis for regulation of ACC activity by polymerization.
Altogether, the findings of this thesis reveal the structural organization of biotin-dependent carboxylase multienzymes, in particular of eukaryotic ACCs. In fungal and human ACC regulation is governed by locking of conformational states either via phosphorylation dependent dynamics or via the formation of activated and inhibited forms of filaments. These insights facilitate novel approaches for inhibition of ACC overactivation in disease by targeting non-enzymatic regions involved in conformational locking.
Advisors:Maier, Timm and Weber-Ban, Eilika
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Structural Biology & Biophysics > Structural Biology (Maier)
UniBasel Contributors:Hagmann, Anna and Maier, Timm
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:12721
Thesis status:Complete
Number of Pages:1 Online-Ressource (167 Seiten)
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Last Modified:08 Feb 2020 14:58
Deposited On:05 Sep 2018 14:22

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