Sodium-23 and lanthanum-139 nuclear magnetic resonance studies of cation binding to aqualysin I,a thermostable serine protease |
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Authors: | Suefuji Kyoko Lin Shie-Jea Wakagi Takayoshi Matsuzawa Hiroshi Yoshimura Etsuro |
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Institution: | Department of Biotechnology, The University of Tokyo, Japan. |
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Abstract: | Aqualysin I has at least two Ca2+-binding sites that have different affinities for Ca2+. The binding of various metal ions to aqualysin I was studied using 23Na- and 139La-NMR spectrometry. Evidence is presented that Ca2+, La3+, and Na+ bind to the low-affinity Ca2+-binding site of aqualysin I, but Mg2+ does not. Our results confirm that binding of metals at the low-affinity Ca2+-binding site is essential for thermostabilization, since the addition of Mg2+ did not result in thermostabilization. La3+ was found to bind to both the low-affinity Ca2+-binding site and an additional metal ion-binding site that can also be involved in the thermostabilization of aqualysin I. |
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