C264W
Contents
Structure-based Mutation Analysis
Mapping onto crystal structure
Side chain properties
Hydrogen Bonding network
Hydrogen bonds are interactions between an hydrogen atom and an electronegative atom. Electronegative atoms which often take part in hydrogen bonds are oxygen, nitrogen and fluorine (not present in amino acid side chains). They serve as a hydrogen bond acceptor, whereas a hydrogen bond donor is a electronegative atom bonded to a hydrogen atom. Hydrogen bonds are essential for the three-dimensional structures of proteins. They play a important role in the formation of helices and beta-sheets and cause proteins to fold into a specific structure.
Showing hydrogen bonds with Pymol: A -> find -> polar contacts -> within selection The respective amino acids were colored by element, s.t. oxygen is red, nitrogen is blue, hydrogen is white and sulfur is yellow.
The following figures show the hydrogen bonds between the wildtype residue and its environment compared to the formation of hydrogen bonds when the corresponding residue is mutated.
Although the amino acids cysteine and tryptophan have very different structures and chemical properties, no change in the hydrogen bonding network occurs (compare Figure 4 and 5).
foldX Energy Comparison
We used the foldX tool to compare the energy of the wildtype protein and the mutated structure. The following table shows the calculated energy values as well as the percentage of difference, to compare the energy calculations with other tools:
Energy | wildtype energy | total energy of mutated protein | difference |
---|---|---|---|
absolute | 401.00 | 488.43 | 87.43 |
relative | 100% | 121% | 21% |
The total energy of the mutated structure is a little bit higher than the energy of the wildtype protein structure. As protein energies should be low for a stable protein, the increasing energy leads to the assumption that this mutation might be damaging for the protein structure.
minimise Energy Comparison
Next we used the minimise tool to compare the energy of the wildtype protein and the mutated structure. The following table shows the calculated energy values as well as the percentage of difference, to compare the energy calculations with other tools:
Energy | wildtype energy | total energy of mutated protein | difference |
---|---|---|---|
absolute | -2485.452755 | -3745.313620 | -1259.860865 |
relative | 100% | 66% | 34% |
The mutated structure has an energy that is much smaller than the wildtype
gromacs Energy comparison
The Gromacs energy comparison was conducted using the AMBER03 force field. The following table shows the calculated energies for the wildtype protein structure.
Energy | Average | Err.Est | RMSD | Tot-Drift (kJ/mol) |
---|---|---|---|---|
Bond | 3072.83 | 2200 | -nan | -13100.2 |
Angle | 3616.97 | 230 | -nan | -1295.57 |
Potential | 2.67001e+07 | 2.6e+07 | -nan | -1.60382e+08 |
Here are the results for the mutated protein structure.
Energy | Average | Err.Est | RMSD | Tot-Drift (kJ/mol) |
---|---|---|---|---|
Bond | 3186.75 | 2300 | -nan | -13603.2 |
Angle | 3831.06 | 370 | -nan | -2070.89 |
Potential | 3.41e+07 | 3.3e+07 | -nan | -2.03e+08 |
As we want to compare the Gromacs energies with the other tools, we calculate the ratio of difference considering the potential energy:
Energy | wildtype energy | total energy of mutated protein | difference |
---|---|---|---|
absolute | 2.67001e+07 | 3.41e+07 | 7399900 |
relative | 100% | 127% | 27% |
The calculated energy for the mutated structure is higher than for the wildtype structure.
Conclusion
return to Structure-based mutation analysis