title: Structural characterization of the regulatory domain of brain carnitine palmitoyltransferase 1.
abstract: Neurons contain a mammalian-specific isoform of the enzyme carnitine palmitoyltransferase 1 (CPT1C) that couples malonyl-CoA to ceramide levels thereby contributing to systemic energy homeostasis and feeding behavior. In contrast to CPT1A, which controls the rate-limiting step of long-chain fatty acid β-oxidation in all tissues, the biochemical context and regulatory mechanism of CPT1C are unknown. CPT1 enzymes are comprised of an N-terminal regulatory domain and a C-terminal catalytic domain (CD) that are separated by two transmembrane helices. In CPT1A, the regulatory domain, termed N, adopts an inhibitory and non-inhibitory state, Nα and Nβ, respectively, which differ in their association with the CD. To provide insight into the regulatory mechanism of CPT1C, we have determined the structure of its regulatory domain (residues Met1-Phe50) by NMR spectroscopy. In relation to CPT1A, the inhibitory Nα state was found to be structurally homologues whereas the non-inhibitory Nβ state was severely destabilized, suggesting a change in overall regulation. The destabilization of Nβ may contribute to the low catalytic activity of CPT1C relative to CPT1A and makes its association with the CD unlikely. In analogy to the stabilization of Nβ by the CPT1A CD, non-inhibitory interactions of N of CPT1C with another protein may exist.
authors.affiliation: Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033.
authors.forename: Soma
authors.initials: S
authors.lastname: Samanta
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Situ
authors.forename: Tobias S
authors.initials: TS
authors.lastname: Ulmer
mesh_terms: D000595:Amino Acid Sequence; D001921:Brain / Q000201:enzymology*; D002334:Carnitine O-Palmitoyltransferase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D004795:Enzyme Stability; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012996:Solutions
chemical_list: D010455:Peptides; D012996:Solutions; D002334:Carnitine O-Palmitoyltransferase
keywords: NMR spectroscopy; allosteric enzymes; energy homeostasis; fatty acid metabolism; membrane proteins
references.citation: Genes Dev. 2011 May 15;25(10):1041-51
references.pmid: 21576264
references.citation: Eur J Biochem. 1997 Feb 15;244(1):1-14
references.pmid: 9063439
references.citation: Mol Genet Metab. 1999 Dec;68(4):424-40
references.pmid: 10607472
references.citation: Annu Rev Nutr. 2006;26:1-22
references.pmid: 16848698
references.citation: J Magn Reson. 1997 Mar;125(1):171-7
references.pmid: 9245376
references.citation: Proc Natl Acad Sci U S A. 1997 Nov 11;94(23):12366-71
references.pmid: 9356455
references.citation: Adv Drug Deliv Rev. 2009 Nov 30;61(14):1353-62
references.pmid: 19716391
references.citation: J Am Chem Soc. 2003 Jul 30;125(30):9179-91
references.pmid: 15369375
references.citation: J Magn Reson. 2000 Mar;143(1):184-96
references.pmid: 10698659
references.citation: J Biomol NMR. 2000 Oct;18(2):101-5
references.pmid: 11101214
references.citation: J Magn Reson. 2003 Jan;160(1):65-73
references.pmid: 12565051
references.citation: Genomics. 2002 Oct;80(4):433-42
references.pmid: 12376098
references.citation: Proc Natl Acad Sci U S A. 2011 Jun 7;108(23):9691-6
references.pmid: 21593415
references.citation: J Biomol NMR. 2009 Aug;44(4):213-23
references.pmid: 19548092
references.citation: Proc Natl Acad Sci U S A. 2006 May 9;103(19):7282-7
references.pmid: 16651524
references.citation: J Am Chem Soc. 2004 Jun 16;126(23):7281-92
references.pmid: 15186165
references.citation: Nucleic Acids Res. 2002 May 15;30(10):e43
references.pmid: 12000848
references.citation: Protein Sci. 1998 Jan;7(1):21-38
references.pmid: 9514257
references.citation: J Biol Chem. 2012 Jun 15;287(25):21224-32
references.pmid: 22539351
references.citation: J Biol Chem. 2008 Mar 14;283(11):6878-85
references.pmid: 18192268
references.citation: Diabetologia. 2009 May;52(5):912-20
references.pmid: 19224198
references.citation: Protein Eng. 1997 Oct;10(10):1131-41
references.pmid: 9488138
references.citation: Biochem J. 1997 May 1;323 ( Pt 3):711-8
references.pmid: 9169604
references.citation: Bioinformatics. 2004 Feb 12;20(3):426-7
references.pmid: 14960472
references.citation: J Biol Chem. 2007 Jun 22;282(25):18212-18224
references.pmid: 17452323
references.citation: Annu Rev Nutr. 2008;28:253-72
references.pmid: 18598135
references.citation: FEBS J. 2011 Feb;278(4):552-8
references.pmid: 21199367
references.citation: J Biol Chem. 2011 Dec 9;286(49):42545-42554
references.pmid: 21990363
references.citation: J Biomol NMR. 2004 Oct;30(2):181-94
references.pmid: 15666562
references.citation: Proteins. 1998 Jun 1;31(4):460-76
references.pmid: 9626705