PIPSA

PIPSA computes pairwise similarity of three-dimensional interaction property fields, focusing on protein electrostatic potentials to analyze determinants of ligand binding and protein–protein interactions.

Key Features:

• Electrostatic potential comparison: Performs objective, quantitative pairwise comparisons of electrostatic potentials among protein sets to infer functional relationships.
• Continuum solvation modeling: Computes molecular electrostatic potentials using a continuum solvation model.
• Poisson–Boltzmann and multipole methods: Solves the Poisson–Boltzmann equation via finite difference or computes potentials analytically by multipole expansion, methods that facilitate rapid comparison across large datasets.
• Comparative modeling: Constructs three-dimensional structures from database sequences using comparative modeling to enable analysis of proteins without experimental structures.
• Model vs experimental assessment: Applies electrostatic comparisons to datasets such as the Pleckstrin homology (PH) domain family (104 members) and assesses agreement between homology models and experimental structures, comparing variations to those from nuclear magnetic resonance data or molecular dynamics simulations.
• Conservation and variation analysis: Detects conserved electrostatic properties and notable exceptions, including PH domains linked to a Db1 homology (DH) domain and proteins with internal PH domain repeats.

Scientific Applications:

• Functional prediction: Uses electrostatic similarity to help predict functional similarities or differences within protein families.
• Structural analysis: Provides insight into the conservation and variation of electrostatic properties across diverse protein sequences for evolutionary and functional interpretation.
• Protein engineering: Identifies conserved electrostatic features that can inform modifications aimed at altering or preserving function and stability.

Methodology:

Computes pairwise similarity of three-dimensional interaction property fields (electrostatic potentials); computes molecular potentials using a continuum solvation model via finite difference solution of the Poisson–Boltzmann equation or analytical multipole expansion; constructs three-dimensional structures from database sequences using comparative modeling.