Structural and thermodynamic responses of mutations at a Ca2+ binding site engineered into human lysozyme.Kuroki, R., Yutani, K.
(1998) J Biol Chem 273: 34310-34315
- PubMed: 9852096
- DOI: 10.1074/jbc.273.51.34310
- Primary Citation of Related Structures:
1I1Z, 1I20, 1I22
- PubMed Abstract:
- Thermodynamic Changes in the Binding of Ca2+ to a Mutant Human Lysozyme (D86/92). Enthalpy-entropy compensation observed upon Ca2+ binding to proteins.
Kuroki, R., Nitta, K., Yutani, K.
(1992) J Biol Chem 267: 24297
- Entropic Stabilization of a Mutant Human Lysozyme Induced by Calcium Binding
Kuroki, R., Kawakita, S., Nakamura, H., Yutani, K.
(1992) Proc Natl Acad Sci U S A 89: 6803
- Crystal Structures of the Apo- and Holomutant Human Lysozymes with an Introduced Ca2+ Binding Site
Inaka, K., Kuroki, R., Kikuchi, M., Matsushima, M.
(1991) J Biol Chem 266: 20666
- Design and Creation of a Ca2+ Binding Site in Human Lysozyme to Enhance Structural Stability
Kuroki, R., Taniyama, Y., Seko, C., Nakamura, H., Kikuchi, M., Ikehara, M.
(1989) Proc Natl Acad Sci U S A 86: 6903
Structural determinants of Ca2+ binding sites within proteins typically comprise several acidic residues in appropriate juxtaposition. Three residues (Ala-83, Gln-86, and Ala-92) in human lysozyme are characteristically mutated to Lys, Asp, and Asp, respectively, in natural Ca2+ binding lysozymes and alpha-lactalbumins ...
Structural determinants of Ca2+ binding sites within proteins typically comprise several acidic residues in appropriate juxtaposition. Three residues (Ala-83, Gln-86, and Ala-92) in human lysozyme are characteristically mutated to Lys, Asp, and Asp, respectively, in natural Ca2+ binding lysozymes and alpha-lactalbumins. The effects of these mutations on the stability and Ca2+ binding properties of human lysozyme were investigated using calorimetry and were interpreted with crystal structures. The double mutant, in which Glu-86 and Ala-92 were replaced with Asp, clearly showed Ca2+ binding affinity, whereas neither point mutant showed Ca2+ affinity, indicating that both residues are essential. The further mutation of Ala-83 --> Lys did not affect the Ca2+ binding of the double mutant. The point mutations Ala-83 --> Lys and Glu-86 --> Asp did not affect the stability, whereas the mutation Ala-92 --> Asp was about 1.3 kcal/mol less stable. Structural analyses showed that both Asp-86 and Lys-83 were exposed to solvent. Side chains of Asp-86 and Asp-91 were rotated in opposite directions about chi1 angle, as if to reduce the electrostatic repulsion. The charged amino acids at the Ca2+ binding site did not significantly affect stability of the protein, possibly because of the local conformational change of the side chains.
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