1GB9: Crystal Structure Of Mutant Human Lysozyme Substituted At The Surface Positions

To evaluate the contribution of the amino acid residues on the surface of a protein to its stability, a series of hydrophobic mutant human lysozymes (Val to Gly, Ala, Leu, Ile, Met, and Phe) modified at three different positions on the surface, which are located in the alpha-helix (Val 110), the beta-sheet (Val 2), and the loop (Val 74), were constructed. Their thermodynamic parameters of denaturation and crystal structures were examined by calorimetry and by X-ray crystallography at 100 K, respectively. Differences in the denaturation Gibbs energy change between the wild-type and the hydrophobic mutant proteins ranged from 4.6 to -9.6 kJ/mol, 2.7 to -1.5 kJ/mol, and 3.6 to -0.2 kJ/mol at positions 2, 74, and 110, respectively. The identical substitution at different positions and different substitutions at the same position resulted in different degrees of stabilization. Changes in the stability of the mutant proteins could be evaluated by a unique equation considering the conformational changes due to the substitutions [Funahashi et al. (1999) Protein Eng. 12, 841-850]. For this calculation, secondary structural propensities were newly considered. However, some mutant proteins were not adapted to the equation. The hydration structures around the mutation sites of the exceptional mutant proteins were affected due to the substitutions. The stability changes in the exceptional mutant proteins could be explained by the formation or destruction of the hydration structures. These results suggest that the hydration structure mediated via hydrogen bonds covering the protein surface plays an important role in the conformational stability of the protein.
PDB ID: 1GB9Download
MMDB ID: 13789
PDB Deposition Date: 2000/6/26
Updated in MMDB: 2017/10
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
Similar Structures:
Biological Unit for 1GB9: monomeric; determined by author
Molecular Components in 1GB9
Label Count Molecule
Protein (1 molecule)
Lysozyme(Gene symbol: LYZ)
Molecule annotation
Chemical (1 molecule)
* Click molecule labels to explore molecular sequence information.

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