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Structures of orthorhombic lysozyme grown at basic pH and its low-humidity variant
N Sukumar1, B K Biswal, M Vijayan
1Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
Summary
Structural analysis of orthorhombic lysozyme reveals no significant pH-dependent changes in molecular geometry. However, low humidity alters C-terminal residues and the hydration shell
Area of Science:
- Biochemistry
- Structural Biology
- Crystallography
Background:
- Lysozyme is a key enzyme in biological systems.
- Understanding protein structure and hydration is crucial for function.
- Previous studies have investigated lysozyme under varying pH conditions.
Purpose of the Study:
- To determine the crystal structure of orthorhombic lysozyme at basic pH.
- To analyze the structural changes in a low-humidity variant of orthorhombic lysozyme.
- To compare the molecular geometry and hydration shell between native and low-humidity forms.
Main Methods:
- X-ray crystallography was used to solve and refine the structures.
- Orthorhombic lysozyme crystals were grown at basic pH.
- A low-humidity variant was prepared and analyzed.
Main Results:
- The structures of native and low-humidity orthorhombic lysozyme were determined at 1.9 and 2.0 A resolution.
- No systematic pH-dependent differences in molecular geometry were observed.
- Changes in molecular geometry were more pronounced in C-terminal residues in the low-humidity form.
- The hydration shell's water molecules shifted, but the shell moved with the protein.
Conclusions:
- Protein structure is generally stable across tested pH ranges.
- Low humidity induces specific conformational changes, particularly in C-terminal regions.
- The hydration shell dynamically adapts to environmental changes, moving with the protein.