Mapping the distribution of conformational information throughout a protein sequence

Area of Science:

• Biochemistry
• Structural Biology
• Protein Science

Background:

• Protein three-dimensional structure is determined by amino acid sequence.
• Identifying essential structure-determining amino acid residues remains challenging.

Purpose of the Study:

• To investigate the role of specific sequence segments in maintaining the overall protein fold.
• To determine if any single segment of the Bacillus licheniformis beta-lactamase (ESBL) sequence is essential for its structure.

Main Methods:

• Production and purification of 25 ESBL variants with deletions of 5-21 contiguous residues.
• Analysis of structural integrity using circular dichroism and size-exclusion chromatography.
• Assessment of functional conformations by measuring catalytic constants.

Main Results:

• Most variants exhibited conformational heterogeneity.
• Despite deletions, all variants populated conformations retaining essential native fold features.
• 82% of the sequence and 92% of non-local atom-atom contacts were eliminated in the variants.

Conclusions:

• No single segment of the ESBL sequence is indispensable for the protein's overall structure.
• Local information and modular organization likely contribute significantly to protein tertiary fold specificity and cooperativity.