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CAMRA: chemical shift based computer aided protein NMR assignments
W Gronwald1, L Willard, T Jellard
1Protein Engineering Network of Centres of Excellence, University of Alberta, Edmonton, Canada.
Journal of Biomolecular NMR
|December 3, 1998
Summary
Computer Aided Magnetic Resonance Assignment (CAMRA) aids protein NMR spectral assignment. This novel method uses predicted chemical shifts and spin systems, offering a unique approach for residue-specific assignments.
Area of Science:
- Biochemistry
- Structural Biology
- Computational Chemistry
Background:
- Protein structure determination using Nuclear Magnetic Resonance (NMR) spectroscopy is crucial for understanding biological function.
- Residue-specific assignment of NMR spectra is a fundamental and often challenging step in this process.
- Existing automated assignment programs often rely on complex connectivity information, limiting their applicability in certain scenarios.
Purpose of the Study:
- To introduce CAMRA (Computer Aided Magnetic Resonance Assignment), a novel suite of programs for automated, residue-specific protein NMR spectral assignment.
- To present a unique approach based on matching predicted chemical shifts with observed spin systems, independent of connectivity data.
- To demonstrate the utility of CAMRA, particularly for challenging cases like flexible protein regions.
Main Methods:
- CAMRA comprises three units: ORB for predicting chemical shifts, CAPTURE for processing NMR spectra and identifying spin systems, and PROCESS for integrating predictions and observations.
- ORB utilizes chemical shift databases of homologous proteins and statistically derived data categorized by residue, atom, and secondary structure.
- The assignment process relies solely on matching predicted shifts with observed spin systems, avoiding the use of NOE (Nuclear Overhauser Effect) or other connectivity information.
Main Results:
- CAMRA successfully performed residue-specific assignments for two medium-sized chemokine proteins.
- The program demonstrated effectiveness when a database of homologous proteins with at least 30% sequence identity was available.
- CAMRA provides ranked assignment choices with associated scores and confidence values.
Conclusions:
- CAMRA offers a new and unique computational approach for protein NMR spectral assignment.
- This method is particularly valuable for assigning flexible regions or when NOE data is limited.
- CAMRA is versatile and can incorporate heteronuclear and three-dimensional NMR experiments, complementing existing assignment strategies.