Improved pK(a) prediction: combining empirical and semimicroscopic methods.

Area of Science:

• Computational chemistry
• Biophysics
• Protein science

Background:

• Accurate prediction of ionizable residue pK(a) values is crucial for understanding protein function and interactions.
• Existing computational methods vary in their accuracy and applicability to different types of pK(a) shifts.

Purpose of the Study:

• To compare the accuracy of three distinct computational methods (KBPLUS, PROPKA, PKAcal) for predicting experimentally determined protein pK(a) values.
• To evaluate the performance of these methods across different ranges of experimental pK(a) shifts.
• To investigate the potential of consensus approaches for improving pK(a) prediction accuracy.

Main Methods:

• Calculation of 171 experimentally known pK(a) values for ionizable residues in 15 proteins using KBPLUS (continuum electrostatic model), PROPKA (empirical, physically motivated), and PKAcal (empirical function).
• Comparison of computed pK(a) values against experimental data using root mean square deviation (RMSD).
• Analysis of method performance based on weakly and strongly shifted experimental pK(a) values.
• Testing of consensus strategies combining predictions from multiple methods.

Main Results:

• PROPKA demonstrated the highest overall accuracy in reproducing experimental pK(a) values.
• PROPKA's accuracy was superior for weakly shifted pK(a) values, while KBPLUS performed comparably for strongly shifted values.
• PKAcal showed poor accuracy for strongly shifted pK(a) values but performed similarly to PROPKA for weakly shifted values.
• Consensus approaches generally improved prediction accuracy compared to individual methods.

Conclusions:

• No single method consistently outperformed others across all pK(a) shift ranges.
• Consensus approaches offer a robust strategy for enhancing the accuracy of protein pK(a) predictions.
• Combining multiple computational methods is recommended for reliable pK(a) value determination in protein studies.