title: Essential role of the metal-ion in the IPM-assisted domain closure of 3-isopropylmalate dehydrogenase.
abstract: X-ray structures of 3-isopropylmalate dehydrogenase (IPMDH) do not provide sufficient information on the role of the metal-ion in the metal-IPM assisted domain closure. Here solution studies were carried out to test its importance. Small-angle X-ray scattering (SAXS) experiments with the Thermus thermophilus enzyme (complexes with single substrates) have revealed only a very marginal (0-5%) extent of domain closure in the absence of the metal-ion. Only the metal-IPM complex, but neither the metal-ion nor the free IPM itself, is efficient in stabilizing the native protein conformation as confirmed by denaturation experiments with Escherichia coli IPMDH and by studies of the characteristic fluorescence resonance energy transfer (FRET) signal (from Trp to bound NADH) with both IPMDHs. A possible atomic level explanation of the metal-effect is given.
authors.affiliation: Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: Eva
authors.initials: E
authors.lastname: Gráczer
authors.forename: Peter V
authors.initials: PV
authors.lastname: Konarev
authors.forename: Tamás
authors.initials: T
authors.lastname: Szimler
authors.forename: András
authors.initials: A
authors.lastname: Bacsó
authors.forename: Adrienn
authors.initials: A
authors.lastname: Bodonyi
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Péter
authors.initials: P
authors.lastname: Závodszky
authors.forename: Mária
authors.initials: M
authors.lastname: Vas
mesh_terms: D050539:3-Isopropylmalate Dehydrogenase / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology; D008670:Metals / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D008670:Metals; D050539:3-Isopropylmalate Dehydrogenase