How far are we from automatic crystal structure solution via molecular-replacement techniques?

Area of Science:

• Structural Biology
• Computational Biology
• Biophysics

Background:

• Molecular replacement is crucial for solving protein and nucleic acid structures.
• Traditional methods often involve solving complex multi-dimensional problems.
• Existing programs like REMO09 subdivide these problems into smaller, manageable steps.

Purpose of the Study:

• To revisit and improve the REMO09 molecular replacement program.
• To implement a novel probabilistic approach for phase determination.
• To enhance the accuracy and efficiency of structure solution.

Main Methods:

• A new probabilistic approach directly derives conditional distribution functions.
• Prior information, including model molecules, is incorporated into the rotation and translation steps.
• Figures of merit are derived for recognizing correct orientation and location.
• Phases are refined and extended in a subsequent pipeline.
• Automated model building is performed using the CAB program.

Main Results:

• The revisited REMO09 successfully implements a direct probabilistic approach.
• Conditional distribution functions are derived without calculating joint probability distributions.
• Figures of merit improve the recognition of correct molecular orientation and translation.
• The pipeline effectively refines phases and generates electron-density maps.
• Automated interpretation of electron-density maps by CAB is demonstrated.

Conclusions:

• The new probabilistic approach in REMO09 offers a more direct and potentially more accurate method for molecular replacement.
• This advancement facilitates automated protein and nucleic acid structure determination.
• The integrated pipeline, including CAB, streamlines the entire structure solution process.