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Essential role of the metal‐ion in the IPM‐assisted domain closure of 3‐isopropylmalate dehydrogenase
Author(s) -
Gráczer Éva,
Konarev Peter V.,
Szimler Tamás,
Bacsó András,
Bodonyi Adrienn,
Svergun Dmitri I.,
Závodszky Péter,
Vas Mária
Publication year - 2011
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2011.09.013
Subject(s) - thermus thermophilus , metal , chemistry , förster resonance energy transfer , metal ions in aqueous solution , crystallography , ion , escherichia coli , small angle x ray scattering , denaturation (fissile materials) , biophysics , fluorescence , biochemistry , scattering , biology , nuclear chemistry , organic chemistry , physics , optics , quantum mechanics , gene
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.