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National Chung Hsing University Institutional Repository - NCHUIR > 生命科學院 > 基因體暨生物資訊學研究所 > 依資料類型分類 > 期刊論文 >  Biophysical Characterization of the Dimer and Tetramer Interface Interactions of the Human Cytosolic Malic Enzyme

Please use this identifier to cite or link to this item: http://nchuir.lib.nchu.edu.tw/handle/309270000/145706

標題: Biophysical Characterization of the Dimer and Tetramer Interface Interactions of the Human Cytosolic Malic Enzyme
作者: Murugan, Sujithkumar;Hung, Hui-Chih
Contributors: Wei Chun Wang
日期: 2012-12-21
Issue Date: 2013-07-02 10:20:17 (UTC+8)
摘要: The cytosolic NADP+-dependent malic enzyme (c-NADP-ME) has a dimer-dimer quaternary structure in which the dimer
interface associates more tightly than the tetramer interface. In this study, the urea-induced unfolding process of the c-
NADP-ME interface mutants was monitored using fluorescence and circular dichroism spectroscopy, analytical
ultracentrifugation and enzyme activities. Here, we demonstrate the differential protein stability between dimer and
tetramer interface interactions of human c-NADP-ME. Our data clearly demonstrate that the protein stability of c-NADP-ME
is affected predominantly by disruptions at the dimer interface rather than at the tetramer interface. First, during thermal
stability experiments, the melting temperatures of the wild-type and tetramer interface mutants are 8–10uC higher than
those of the dimer interface mutants. Second, during urea denaturation experiments, the thermodynamic parameters of the
wild-type and tetramer interface mutants are almost identical. However, for the dimer interface mutants, the first transition
of the urea unfolding curves shift towards a lower urea concentration, and the unfolding intermediate exist at a lower urea
concentration. Third, for tetrameric WT c-NADP-ME, the enzyme is first dissociated from a tetramer to dimers before the 2 M
urea treatment, and the dimers then dissociated into monomers before the 2.5 M urea treatment. With a dimeric tetramer
interface mutant (H142A/D568A), the dimer completely dissociated into monomers after a 2.5 M urea treatment, while for a
dimeric dimer interface mutant (H51A/D90A), the dimer completely dissociated into monomers after a 1.5 M urea
treatment, indicating that the interactions of c-NADP-ME at the dimer interface are truly stronger than at the tetramer
interface. Thus, this study provides a reasonable explanation for why malic enzymes need to assemble as a dimer of dimers.
Relation: PLoS ONE, Volume 7, Issue 12
Appears in Collections:[依資料類型分類] 期刊論文

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