Sunday, 31 October 2021

Multiple sequence alignments

A sequence alignment is a rather important tool.
  • Sequence conservation is a key ingredient in most nucleotide mutation severity predictors.
  • The covariance within it powers the AlphaFold2 Evoformer and other de novo structure predictors.
  • The phylogeny extracted from it tells the evolutionary tale of the protein
However, on the very basic level, i.e. getting a nice figure, far from the world of covariance matrices, it is a slight nuisance.
Therefore I would like share some pointers on choosing species and two python operation, namely getting the equivalent residue in a homologue and making a figure in Plotly. Just like with docking, where careful and diligent human choices make all the difference, rational choices help greatly with clarity for sequence alignments.

Sunday, 17 October 2021

Filling missing loops by cannibalising AlphaFold2

I could not resist this Photoshop.
But the process is not as dramatic
and the results not as bad as Temple of Doom...
If done right.
AlphaFold2 models have a complete sequence, but for innumerable reasons the crystal structure of the protein is better, but may have missing spans. As a result one may want, for illustrative purposes only, to rip out the required parts from the AlphaFold2 models (as fragments) and have them built into the target structure. Here is how to do it by threading.