ICM-Homology

ICM-Pro Homology Module is an add-on to Molsoft's ICM-Pro platform, providing a robust and well-validated homology modeling solution for computational structural biologists, medicinal chemists, and drug discovery researchers. The module enables the construction of high-quality 3D protein models from sequence data by leveraging template structures, and has demonstrated excellent accuracy in blind predictions at the CASP2 competition as well as numerous protein engineering applications.

The underlying algorithm places the aligned polypeptide chain onto a template structure and then predicts side-chain torsion angles through simultaneous global optimization of energy for all non-identical residues. Conformational modeling relies on an internal coordinate definition of the molecular object combined with the computationally efficient ICM Biased Probability Monte Carlo (BPMC) optimization. The extended force field incorporates surface terms, electrostatics solved via the boundary element solution of the Poisson equation, side-chain entropy terms, and a fast molecular surface calculation algorithm. Model quality is assessed by a specialized ICM procedure that also predicts possible backbone deviations between homologues. Notably, ICM models built with as little as 35% sequence identity have proven accurate enough for receptor-based rational drug design.

Key Features and Capabilities

• Sensitive sequence search for template identification
• Fast model building — constructs the full model including all loops in seconds
• Loop prediction using a loop PDB database
• Loop prediction through local energy optimization
• Multi-template modeling for improved model accuracy
• Loop grafting to transfer loop conformations between structures
• Protein sculpting for manual structural editing and refinement
• Peptide modeling support
• Search the PDB for similar loop conformations
• Calculation of relative residue frequency in similar loops from the PDB
• Prediction of disulfide bonds
• Local reliability prediction and comprehensive model validation features
• Model refinement using ICM global optimization
• Membrane protein modeling
• High-throughput homology modeling for large-scale projects

Validated Applications

• In silico discovery of novel Retinoic Acid Receptor agonist structures
• Structural modeling of nicotinic acetylcholine receptor isotypes
• Nuclear hormone receptor targeted virtual screening
• Discovery of diverse thyroid hormone receptor antagonists by high-throughput docking
• Rational discovery of novel nuclear hormone receptor antagonists
• Protein engineering studies including design and characterization of stable monomeric proteins
• Modeling and mutagenesis of conserved phosphate-binding loops for substrate specificity studies

ICM-Pro Homology Module is delivered as an integrated add-on within the ICM-Pro environment, allowing seamless combination of homology modeling with other ICM-Pro capabilities such as docking and virtual screening. Its proven track record across peer-reviewed publications and competitive benchmarks makes it a reliable choice for structure-based drug design pipelines in both academic and pharmaceutical research settings.