Structural effects of monovalent anions on polymorphic lysozyme crystals

Area of Science:

• Structural Biology
• Biochemistry
• Crystallography

Background:

• Protein crystal polymorphism affects drug development and structural studies.
• Understanding the role of salts (ions) in crystal formation is crucial for controlling polymorphism.

Purpose of the Study:

• To investigate the direct effects of various salts on protein crystal polymorphism.
• To map the interaction sites of monovalent anions with different lysozyme crystal forms.

Main Methods:

• X-ray crystallography was used to determine four new hen egg-white lysozyme structures.
• Comparison of new and previously published lysozyme structures with different crystal forms (triclinic, monoclinic, tetragonal, orthorhombic).
• Analysis of anion binding sites across diverse lysozyme crystal structures.

Main Results:

• Four new hen egg-white lysozyme structures were determined in the presence of NapTS, NaI, NaNO(3), and KSCN.
• A comprehensive mapping of monovalent anion interactions (nitrate, chloride, iodide, bromide, thiocyanate) with lysozyme surfaces was created.
• Common anion binding sites were identified across different crystal forms and anion types.

Conclusions:

• Anion binding sites can be conserved across various lysozyme crystal forms.
• Specific anion binding sites are influenced by crystal packing geometry and local charge environment.
• Salt selection is a critical factor in controlling protein crystal polymorphism.