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
- Primary Citation of Related Structures:  1I20, 1I22
- PubMed Abstract:
- Entropic Stabilization of a Mutant Human Lysozyme Induced by Calcium Binding
Kuroki, R.,Kawakita, S.,Nakamura, H.,Yutani, K.
(1992) Proc.Natl.Acad.Sci.USA 89: 6803
- Crystal Structure 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.,Taniyam, Y.,Seko, C.,Nakamura, H.,Kikuchi, M.,Ikehara, M.
(1989) Proc.Natl.Acad.Sci.USA 86: 6903
- 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
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, ...
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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