title: Metal ions stabilize a dimeric molten globule state between the open and closed forms of malic enzyme.
abstract: Malic enzyme is a tetrameric protein with double dimer quaternary structure. In 3-5 M urea, the pigeon cytosolic NADP(+)-dependent malic enzyme unfolded and aggregated into various forms with dimers as the basic unit. Under the same denaturing conditions but in the presence of 4 mM Mn(2+), the enzyme existed exclusively as a molten globule dimer in solution. Similar to pigeon enzyme (Chang, G. G., T. M. Huang, and T. C. Chang. 1988. Biochem. J. 254:123-130), the human mitochondrial NAD(+)-dependent malic enzyme also underwent a reversible tetramer-dimer-monomer quaternary structural change in an acidic pH environment, which resulted in a molten globule state that is also prone to aggregate. The aggregation of pigeon enzyme was attributable to Trp-572 side chain. Mutation of Trp-572 to Phe, His, Ile, Ser, or Ala abolished the protective effect of the metal ions. The cytosolic malic enzyme was completely digested within 2 h by trypsin. In the presence of Mn(2+), a specific cutting site in the Lys-352-Gly-Arg-354 region was able to generate a unique polypeptide with M(r) of 37 kDa, and this polypeptide was resistant to further digestion. These results indicate that, during the catalytic process of malic enzyme, binding metal ion induces a conformational change within the enzyme from the open form to an intermediate form, which upon binding of L-malate, transforms further into a catalytically competent closed form.
authors: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.
authors: Hui-Chuan
authors: HC
authors: Chang
authors: Liang-Yu
authors: LY
authors: Chen
authors: Yi-Hang
authors: YH
authors: Lu
authors: Meng-Ying
authors: MY
authors: Li
authors: Yu-Hou
authors: YH
authors: Chen
authors: Chao-Hsiung
authors: CH
authors: Lin
authors: Gu-Gang
authors: GG
authors: Chang
mesh_terms: D004795:Enzyme Stability; D008291:Malate Dehydrogenase / Q000737:chemistry* / Q000648:ultrastructure*; D008670:Metals / Q000737:chemistry*; D044367:Phase Transition; D011487:Protein Conformation; D017510:Protein Folding
chemical_list: D008670:Metals; D008291:Malate Dehydrogenase; C495394:malic enzyme 2; human
references: Biochemistry. 2004 Jun 15;43(23):7382-90
references: 15182181
references: FASEB J. 1996 Jan;10(1):102-9
references: 8566530
references: Structure. 1999;7(8):877-889
references: 10467136
references: Proteins. 2004 Feb 15;54(3):404-11
references: 14747989
references: Biochem J. 1988 Aug 15;254(1):123-30
references: 3140794
references: FEBS J. 2005 Dec;272(23):5962-70
references: 16302961
references: Biochemistry. 2002 Jun 4;41(22):6928-38
references: 12033925
references: J Biol Chem. 2003 Jun 27;278(26):23996-4002
references: 12711612
references: Curr Top Cell Regul. 1975;9:157-81
references: 235406
references: Protein Eng. 1997 Oct;10(10):1205-11
references: 9488145
references: Curr Opin Struct Biol. 2006 Feb;16(1):68-70
references: 16443362
references: J Biol Chem. 1967 Nov 25;242(22):5315-22
references: 4383636
references: Trends Biochem Sci. 2003 Jan;28(1):18-25
references: 12517448
references: Biophys J. 2000 Mar;78(3):1606-19
references: 10692345
references: Eur J Biochem. 1994 Nov 1;225(3):1021-7
references: 7525283
references: Biochem J. 2005 Nov 15;392(Pt 1):39-45
references: 15989682
references: Electrophoresis. 1997 Dec;18(15):2714-23
references: 9504803
references: Q Rev Biophys. 1996 Feb;29(1):1-90
references: 8783394
references: Protein Sci. 2002 Feb;11(2):332-41
references: 11790843
references: Biochemistry. 2004 Sep 14;43(36):11361-70
references: 15350123
references: Biochemistry. 2000 Nov 21;39(46):14095-102
references: 11087357
references: Structure. 2002 Jul;10(7):951-60
references: 12121650
references: Nat Struct Biol. 2000 Mar;7(3):251-7
references: 10700286
references: J Biol Chem. 2003 Sep 26;278(39):38051-8
references: 12853453
references: Biochem Biophys Res Commun. 2000 Aug 2;274(2):440-4
references: 10913357
references: Biochemistry. 2003 Aug 19;42(32):9712-21
references: 12911313
references: Adv Protein Chem. 1995;47:83-229
references: 8561052
references: Biochim Biophys Acta. 1977 Aug 11;483(2):228-35
references: 19063
references: Protein Sci. 1993 Nov;2(11):1844-52
references: 8268795
references: Biochemistry. 2003 Nov 11;42(44):12721-33
references: 14596586
references: J Biol Chem. 2002 Feb 15;277(7):4663-71
references: 11739398
references: Nucleic Acids Res. 2004 Jul 1;32(Web Server issue):W668-73
references: 15215473
references: Trends Biochem Sci. 2005 Jan;30(1):13-9
references: 15653321
references: Mol Cell Biochem. 1982 Mar 5;43(1):3-26
references: 7078548
references: Biochemistry. 2005 Sep 27;44(38):12737-45
references: 16171388