Stabilization of protein structure through π–π interaction in the second coordination sphere of pseudoazurin |
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| Authors: | Takahide Yamaguchi Yuko Nihei Duncan E. K. Sutherland Martin J. Stillman Takamitsu Kohzuma |
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| Affiliation: | 1. Graduate School of Science and Engineering, Institute of Quantum Beam Science, Ibaraki University, Mito, Ibaraki, Japan;2. Department of Biology, The University of Western Ontario, London, Ontario, Canada;3. Department of Chemistry, The University of Western Ontario, London, Ontario, Canada |
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| Abstract: | Noncovalent, weak interactions in the second coordination sphere of the copper active site of Pseudoazurin (PAz) from Achromobacter cycloclastes were examined using a series of Met16X variants. In this study, the differences in protein stability due to the changes in the nature of the 16th amino acid (Met, Phe, Val, Ile) were investigated by electrospray ionization mass spectrometry (ESI‐MS) and far‐UV circular dichroism (CD) as a result of acid denaturation. The percentage of native states (folded holo forms) of Met16Phe variants was estimated to be 75% at pH 2.9 although the wild‐type (WT), Met16Val and Met16Ile PAz, became completely unfolded. The high stability under acidic conditions is correlated with the result of the active site being stabilized by the aromatic substitution of the Met16 residue. The π–π interaction in the second coordination sphere makes a significant contribution to the stability of active site and the protein matrix. |
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| Keywords: | noncovalent weak interaction second coordination sphere blue copper protein ESI‐MS |
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