IHMValidation: Assessment of Integrative Structure Models Deposited to the Protein Data Bank

Area of Science:

• Structural Biology
• Biophysics
• Computational Biology

Background:

• The Protein Data Bank (PDB) archives biomolecular structures, including integrative/hybrid models (PDB-IHM) with diverse representations and experimental data.
• Accurate interpretation of these models requires rigorous assessment of data quality, consistency, and positional uncertainty.
• PDB-IHM currently contains 374 entries, utilizing multi-scale/multi-state representations and 17 experimental data types.

Purpose of the Study:

• To introduce the IHMValidation pipeline for assessing the quality of integrative/hybrid structure models.
• To provide a standardized reporting system for model quality and data validation.
• To incorporate recommendations from the Worldwide Protein Data Bank (wwPDB) Integrative Methods Task Force and specific experimental communities.

Main Methods:

• Developed the IHMValidation pipeline, accessible at https://validate.pdb-ihm.org and https://github.com/salilab/IHMValidation.
• Integrated recommendations from the wwPDB Integrative Methods Task Force, small-angle scattering (SAS), chemical crosslinking mass spectrometry (crosslinking-MS), and cryo-electron microscopy/tomography (3DEM) communities.
• The pipeline generates a comprehensive IHMValidation report in PDF and HTML formats.

Main Results:

• The IHMValidation report includes six key sections: overview, model details, data quality, local geometry, fit to generation data, and fit to validation data.
• The pipeline assesses consistency between the structure model and the input experimental data.
• It evaluates local geometry and provides estimates of positional uncertainty for model components.

Conclusions:

• The IHMValidation pipeline offers a robust framework for quality assessment of integrative/hybrid models.
• Future expansions will incorporate additional experimental methods (FRET, HDX-MS) and advanced validation criteria.
• This tool enhances the reliability and interpretability of complex biomolecular structure models archived in the PDB.