CAB-align

CAB-align aligns protein structures by comparing residue-residue contact areas to identify residue-level homology while accounting for protein flexibility.

Key Features:

• Flexibility consideration: Focuses on contact areas to capture protein flexibility evident in loop regions, rearrangements between secondary structure elements, and domain-wide conformational changes.
• Residue-level homology identification: Identifies homologous relationships at the residue level by analyzing physical contacts between residues rather than relying solely on 3D coordinates.
• Two-step alignment process: Performs an initial rigid-body alignment using local and global 3D structure superposition followed by iterative dynamic programming to refine alignments.
• Performance evaluation: Assesses performance using four criteria: agreement with gold-standard alignments; alignment quality reflecting evolutionary relationships without 3D coordinate superposition; consistency across multiple alignments; and classification agreement with established standards.
• Benchmark comparisons: Compared against TM-align, FATCAT, and DaliLite and reported to produce high-coverage, accurate alignments and to distinguish homologous from nonhomologous protein pairs in single- and multi-domain comparisons.

Scientific Applications:

• Structural homology detection: Detects residue-level homology between related protein structures for evolutionary analysis.
• Protein dynamics and conformational analysis: Analyzes conformational changes and flexible regions by emphasizing contact-area relationships.
• Classification of homologous versus nonhomologous pairs: Supports discrimination and classification of protein pairs based on contact-derived alignments.
• Single- and multi-domain comparisons: Applies to both single-domain and multi-domain protein structure comparisons to assess structural and evolutionary relationships.

Methodology:

Uses residue-residue contact-area comparison, performs an initial rigid-body alignment via local and global 3D structure superposition, refines alignments with iterative dynamic programming, and evaluates performance against gold-standard alignments and by comparison to TM-align, FATCAT, and DaliLite.