1I1Z

MUTANT HUMAN LYSOZYME (Q86D)

Summary for 1I1Z

• Entry DOI: 10.2210/pdb1i1z/pdb
• Related: 1I20 1I22 1LZ1 2LHM 3LHM
• Descriptor: LYSOZYME C (2 entities in total)
• Functional Keywords: calcium binding site, mutant human lysozyme, hydrolase
• Biological source: Homo sapiens (human)
• Cellular location: Secreted: P61626
• Total number of polymer chains: 1
• Total formula weight: 14707.65

Authors

Kuroki, R. (deposition date: 2001-02-05, release date: 2001-02-28, Last modification date: 2024-10-30)

Primary citation

Kuroki, R.,Yutani, K.
Structural and thermodynamic responses of mutations at a Ca2+ binding site engineered into human lysozyme.
J.Biol.Chem., 273:34310-34315, 1998

PubMed Abstract: 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.

PubMed: 9852096
DOI: 10.1074/jbc.273.51.34310

Experimental method

X-RAY DIFFRACTION (1.8 Å)