xMDFF: molecular dynamics flexible fitting of low-resolution X-ray structures.

Area of Science:

• Structural Biology
• Biophysics

Background:

• X-ray crystallography is key for atomic structure determination.
• Low-resolution data limits detailed analysis of large biological systems.

Purpose of the Study:

• Introduce xMDFF, a novel method for refining atomic models using low-resolution crystallographic data.
• Enable detailed structural analysis of large biomolecules where high-resolution data is unavailable.

Main Methods:

• xMDFF utilizes molecular dynamics flexible fitting (MDFF) and real-space refinement.
• Atomic models are flexibly fit into iteratively updated electron-density maps.
• The method accommodates large-scale model deformations to match low-resolution density.

Main Results:

• xMDFF successfully refined synthetic low-resolution maps of D-ribose-binding protein.
• Applied to six existing low-resolution Protein Data Bank entries, improving structural details.
• Validated the first all-atom structure of voltage-sensing protein Ci-VSP using data from 3.6 to 7 Å resolution.

Conclusions:

• xMDFF is effective for determining atomic structures from low-resolution crystallographic data.
• This method advances structural biology by enabling detailed analysis of challenging systems.
• The validated Ci-VSP structure provides new insights into voltage-sensing mechanisms.