RDC-PANDA

RDC-PANDA integrates residual dipolar couplings (RDCs) and nuclear Overhauser effect (NOE) data from NMR spectroscopy to determine and refine high-resolution protein structures and resolve NOE assignment ambiguities.

Key Features:

• Use of RDCs as global restraints: Employs residual dipolar couplings (RDCs) as global orientational restraints to guide backbone orientations of secondary structure elements (SSEs).
• RDC-EXACT: Solves quartic RDC equations (Wang and Donald) to calculate optimal backbone dihedral angles for each SSE via a systematic search of possible solutions.
• PACKER: Conducts exhaustive searches over all possible SSE backbone conformations constrained by a limited set of unambiguous inter-SSE NOEs identified from chemical shift information.
• HANA (Hausdorff-based NOE Assignment): Uses a Hausdorff-based scoring function to compare experimental NMR spectra with back-calculated NOE patterns and selects position-specific rotamers from a rotamer library to refine ambiguous NOE assignments.
• Local minimization: Applies local minimization to refine loop regions and side-chain conformations while maintaining the core SSE arrangement rigid.
• Rotamer library usage: Leverages a diverse rotamer library for side-chain conformation selection during NOE assignment refinement.
• Ambiguity reduction: Resolves NOE assignment ambiguity by integrating RDC-derived orientations with NOE pattern matching.

Scientific Applications:

• Structure determination from limited NOE datasets: Enables high-resolution protein structure determination and NOE assignment refinement using limited NOE data combined with RDCs.
• Case studies: Applied to FF Domain 2 of human transcription elongation factor CA150, human ubiquitin, the ubiquitin-binding zinc finger domain of human Y-family DNA polymerase Eta (pol eta UBZ), and the human Set2-Rpb1 interacting domain (hSRI).

Methodology:

Computational steps explicitly include solving quartic RDC equations (Wang and Donald) to obtain SSE backbone dihedrals (RDC-EXACT), exhaustive SSE backbone conformation searches constrained by unambiguous inter-SSE NOEs from chemical shifts (PACKER), Hausdorff-based scoring comparing experimental and back-calculated NOE patterns with rotamer library selection for side-chains (HANA), followed by local minimization of loops and side-chains while keeping the core rigid.