Human Keto Acyl Reductase
From Proteopedia
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| - | + | <StructureSection load='4cqm' size='240' side='right' caption='Human ketoacyl reductase complex with NADP (PDB code [[4cqm]])' scene=''> | |
| - | <StructureSection load='4cqm' size='240' side='right' caption=' | + | |
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| - | == Function == | + | __TOC__ |
| + | ==Function== | ||
| + | The mitochondrial fatty acid synthesis (mtFAS) pathway generates precursors for mitochondrally generated alpha-lipoic acids. Defeciency of mtFAS leads to respiratory chain defects and mitochondrial dysfunction. The mtFAS has four enzymatic steps, catalyzed by four different enzymes. Ketoacyl acyl-carrier-protein (ACP) reductase (KAR) catalyzes the second step of mtFAS pathway, where 3-ketoacyl-ACP is reduced to 3R-hydroxyacyl-ACP utilizing NADPH as cofactor. KAR is a heterotetrameric complex made from two different polypeptides: 17β-hydroxysteroid dehydrogenase type 8 (HSD17B8 or KE6, α-subunit) and carbonyl reductase type 4 (CBR4 or SDR45C1, β-subunit)9. <ref>PMID:25203508</ref> | ||
| - | == Disease == | + | See also [[Hydroxysteroid dehydrogenase]]. |
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| + | ==Disease== | ||
| + | Deficiency of the KAR or mtFAS pathway leads to respiratory chain defects and mitochondrial dysfunction in eukaryotes. | ||
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| + | ==Relevance== | ||
| + | All other mtFAS enzymes identified so far are encoded by a single gene while KAR complex is encoded by two different genes HSD17B8 and CBR4.Both subunits complement each other to form a stable quaternary structure as seen in the crystal structure. Further, the functional studies suggest that CBR4 is the functional subunit of KAR. Whereas, HSD17B8 works as a scaffold protein to facilitate the function and stability of KAR. HSD17B8 may works as an auxiliary fatty acid beta oxidation enzymes for the oxidation of 3R-hydroxyacyl-CoA metabolites. | ||
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| + | ==Structural highlights== | ||
| + | Crystal structure of human mitochondrial heteroterameric KAR is solved at 2.34 Å. The co-factors NAD is selectively bound to the HSD17B8 subunits whereas NADP is bound to the CBR4 subunits. Both NAD and NADP are stabilized by several conserved hydrogen bonding interactions in their respective binding sites. The Asp42, Arg12 and Arg 34 are the crucial residues for co-factor recognition. Acetate ion is also bound near NAD, which identifies the fatty acyl chain binding pocket. Ser 135, Tyr148 and Lys152 in CBR4 subunit are the catalytic triad residues involved in the catalysis. <ref>PMID:25203508</ref> | ||
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| + | <scene name='80/809823/Cofactors/1'>Cofactors</scene> are bound to the each subunit. <scene name='80/809823/Nad-a/2'>NAD</scene> is bound in HSD17B8 subunit. <scene name='80/809823/Nadp-c/1'>NADP</scene> is bound to the CBR4 subunit. <scene name='80/809823/Ethanediol/2'>1,2-Ethanediol</scene> is bound near the NAD binding site. <scene name='80/809823/Glycerol/2'>Glycerol</scene> is also bound in the structure. | ||
| - | == Relevance == mtFAS provides the precursor of mitochondrially synthesized α-lipoic acid, a key cofactor for oxidative decarboxylation of α-keto acids and glycine within eukaryotic cells5. There is evidence for other physiologically relevant products of mtFAS in yeast6. Deficiency of mtFAS leads to respiratory chain defects and mitochondrial dysfunction | ||
| - | == Structural highlights == | ||
| - | <scene name='80/809823/All_nadp/2'>NADP</scene> is bound in each of the four subunits in heterotetrameric structure. <scene name='80/809823/Glycerol/1'>glycerol</scene> is also bound in the structure. | ||
This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes. | This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes. | ||
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</StructureSection> | </StructureSection> | ||
== References == | == References == | ||
| - | < | + | <References> |
Current revision
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References
- ↑ Venkatesan R, Sah-Teli SK, Awoniyi LO, Jiang G, Prus P, Kastaniotis AJ, Hiltunen JK, Wierenga RK, Chen Z. Insights into mitochondrial fatty acid synthesis from the structure of heterotetrameric 3-ketoacyl-ACP reductase/3R-hydroxyacyl-CoA dehydrogenase. Nat Commun. 2014 Sep 9;5:4805. doi: 10.1038/ncomms5805. PMID:25203508 doi:http://dx.doi.org/10.1038/ncomms5805
- ↑ Venkatesan R, Sah-Teli SK, Awoniyi LO, Jiang G, Prus P, Kastaniotis AJ, Hiltunen JK, Wierenga RK, Chen Z. Insights into mitochondrial fatty acid synthesis from the structure of heterotetrameric 3-ketoacyl-ACP reductase/3R-hydroxyacyl-CoA dehydrogenase. Nat Commun. 2014 Sep 9;5:4805. doi: 10.1038/ncomms5805. PMID:25203508 doi:http://dx.doi.org/10.1038/ncomms5805
