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Pitfalls in the interpretation of structural changes in mutant proteins from crystal structures
P R Pokkuluri1, X Yang, Y Y Londer
1Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, USA.
Protein crystal packing, not mutation, caused distant structural changes in PpcA protein mutants. Careful analysis of crystal lattice is crucial to avoid misinterpreting structural data.
Area of Science:
- Protein crystallography
- Structural biology
- Biochemistry
Background:
- PpcA protein contains three covalently bound hemes.
- Mutations in proteins can cause structural changes.
- Crystal packing can influence observed protein structures.
Purpose of the Study:
- To investigate the cause of unexpected structural deviations in PpcA mutants.
- To determine if mutations affect distant parts of the protein molecule.
- To highlight the importance of crystal lattice in structural analysis.
Main Methods:
- X-ray crystallography
- Analysis of crystal packing
- Comparison of native and mutant PpcA structures
Main Results:
- Single mutations at residue 58 in PpcA led to structural deviations.
- These deviations were primarily due to crystal packing interactions, not direct mutation effects.
- The mutation site was near another protein molecule in the crystal lattice, causing adjustments.
Conclusions:
- Observed structural changes in PpcA mutants were artifacts of crystal packing.
- It is essential to consider crystal lattice effects when interpreting structural data.
- Misinterpretation of Protein Data Bank coordinates can lead to erroneous conclusions about mutation effects.
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