title: Insights into mitochondrial fatty acid synthesis from the structure of heterotetrameric 3-ketoacyl-ACP reductase/3R-hydroxyacyl-CoA dehydrogenase.
abstract: Mitochondrial fatty acid synthesis (mtFAS) is essential for respiratory growth in yeast and mammalian embryonic survival. The human 3-ketoacyl-acyl carrier protein (ACP) reductase (KAR) of mtFAS is a heterotetrameric α2β2-assembly composed of 17β-hydroxysteroid dehydrogenase type-8 (HSD17B8, α-subunit) and carbonyl reductase type-4 (CBR4, β-subunit). Here we provide a structural explanation for the stability of the heterotetramer from the crystal structure with NAD(+) and NADP(+) bound to the HSD17B8 and CBR4 subunits, respectively, and show that the catalytic activity of the NADPH- and ACP-dependent CBR4 subunit is crucial for a functional HsKAR. Therefore, mtFAS is NADPH- and ACP dependent, employing the 3R-hydroxyacyl-ACP intermediate. HSD17B8 assists in the formation of the competent HsKAR assembly. The intrinsic NAD(+)- and CoA-dependent activity of the HSD17B8 subunit on the 3R-hydroxyacyl-CoA intermediates may indicate a role for this subunit in routing 3R-hydroxyacyl-CoA esters, potentially arising from the metabolism of unsaturated fatty acids, into the mitochondrial β-oxidation pathway.
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland.
authors.forename: Rajaram
authors.initials: R
authors.lastname: Venkatesan
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland.
authors.forename: Shiv K
authors.initials: SK
authors.lastname: Sah-Teli
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland.
authors.forename: Luqman O
authors.initials: LO
authors.lastname: Awoniyi
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Jiang
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Prus
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Kastaniotis
authors.affiliation: 1] Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland [2] State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, China.
authors.forename: J Kalervo
authors.initials: JK
authors.lastname: Hiltunen
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, PO Box 5400, Oulu FI-90014, Finland.
authors.forename: Rik K
authors.initials: RK
authors.lastname: Wierenga
authors.affiliation: State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, China.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Chen
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D064431:3-Oxoacyl-(Acyl-Carrier-Protein) Reductase / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D018360:Crystallography, X-Ray; D057075:Enzyme Assays; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005227:Fatty Acids / Q000096:biosynthesis*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D011506:Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005227:Fatty Acids; C102228:HSD17B8 protein, human; D024101:Mitochondrial Proteins; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D010088:Oxidoreductases; D015094:3-Hydroxyacyl CoA Dehydrogenases; D064431:3-Oxoacyl-(Acyl-Carrier-Protein) Reductase; C533692:CBR4 protein, human; D016660:NAD(P)H Dehydrogenase (Quinone)