Structure of dethiobiotin synthetase at 0.97 A resolution

Area of Science:

• Structural Biology
• Biochemistry
• Crystallography

Background:

• Dethiobiotin synthetase (DTBS) is a key enzyme in biotin biosynthesis.
• Understanding enzyme structure is crucial for elucidating reaction mechanisms.
• Cryo-crystallography is a common technique for studying enzyme structures at low temperatures.

Purpose of the Study:

• To determine the high-resolution crystal structure of dethiobiotin synthetase from Escherichia coli at 100 K.
• To analyze the protein's structural features, including hydrogen bonding and solvent interactions.
• To compare the low-temperature structure with room-temperature data to identify potential structural changes.

Main Methods:

• X-ray diffraction data collection at 0.97 Å resolution and 100 K.
• Refinement of the 224-residue protein structure using SHELX97 with anisotropic displacement parameters.
• Analysis of stereochemistry, hydrogen bonds, and protein-solvent interactions.

Main Results:

• A high-resolution (0.97 Å) crystal structure of dethiobiotin synthetase was refined.
• Frequent C-H…O hydrogen bonds were identified, including within the central β-sheet.
• Comparison with room-temperature structures revealed conformational differences, particularly in active site regions, suggesting potential artifacts from flash-freezing.

Conclusions:

• The detailed 100 K structure of dethiobiotin synthetase provides insights into its atomic-level organization.
• The prevalence of C-H…O interactions highlights their potential role in protein structure and function.
• Observed conformational changes upon cooling raise questions about the validity of cryo-crystallography for studying dynamic enzymatic mechanisms.