Human glycine N-methyltransferase is unfolded by urea through a compact monomer state

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• 作者：Luka ; Zigmund ; Wagner ; Conrad
• 关键词：Glycine N-methyltransferase ; Unfolding ; Dissociation ; Inactivation ; Stability ; Conformation
• 刊名：Archives of Biochemistry and Biophysics
• 出版年：2003
• 出版时间：December 1, 2003
• 年：2003
• 卷：420
• 期：1
• 页码：153-160
• 全文大小：236 K

文摘

Human recombinant glycine N-methyltransferase (GNMT) unfolding by urea was studied by enzyme activity, size-exclusion chromatography, fluorescence spectroscopy, and circular dichroism. Urea unfolding of GNMT is a two-step process. The first transition is a reversible dissociation of the GNMT tetramer to compact monomers in 1.0–3.5M urea with enzyme inactivation. The compact monomers were characterized by Stokes radius (R_s) of 40.7Å equal to that of globular proteins with the same molecular mass as GNMT monomers, absence of exposure of tryptophan residues into solvent, and presence of about 50 % of secondary structure of native protein. The second step of GNMT unfolding is a reversible transition of monomers from compact to a fully unfolded state with R_s of 50Å, exposed tryptophan residues, and disrupted secondary structure in 8M urea.