map_align

!!! UNDER DEVELOPMENT !!!

map_align takes two contact maps and returns an alignment that attempts to maximize the number of overlapping contacts while minimizing the number of gaps [1].

Download and Installation

git clone https://github.com/gjoni/map_align
cd map_align
make

Usage

Options:  -s alignment.a3m               - input, required
          -c contacts.txt                - input, required

          -L list.txt with template IDs  - input, required
          -O prefix for saving top hits  - output, optional
          -N number of top hits to save    10
          -T TM-score cleaning cut-off     0.80
          -M max template size             1000

          -I number of DP iterations       10
          -t number of threads             1

More details on some options:

• -M MAX templates with more than MAX residues will be skipped (longer templates could take much more time to be aligned)

• -T TM top N partial hits will be cleaned to exclude structurally similar matches: if two hits from the scan stage are similar with TM-score > TM then only one (with the higher alignment score) will appear in the final pool

• -O PREFIX top models will be saved as <PREFIX><TEMPLATE_ID>.pdb and <PREFIX><TEMPLATE_ID>.ali where TEMPLATE_ID is an ID from the list file

List of temlates

List of templates is a text file with one entry per line. IDs of the templates are used in output and should not be longer than 10 characters.

/path/to/template1.pdb ID1
/path/to/template2.pdb ID2
...

Contact map format

Contact map is a list of residue-residue pairs in the following format (similar to CASP RR format):

i  j  d1  d2  p

• i, j - indices of the two residues in contact
• d1, d2 - distance limits defining a contact (currently not used)
• p - probability of the contact, should be in the range (0;1]

Examples

cd example
tar xf ecod70.tar.gz

Align a contact map to a library of templates (simplest call):

../map_align -s T0806.a3m -c T0806.con -L ecod70.list

Align a contact map to a library of templates saving top 5 hits at TM-score=70% identity cut-off and running the program on 4 cores (takes ~7 minutes on i5):

../map_align -s T0806.a3m -c T0806.con -L ecod70.list -N 5 -T 0.70 -t 4 -O T0806.

Acknowledgements

This package is a reimplementation of the original map_align program by S.Ovchinnikov [1] to allow for:

• direct use of PDB files as templates
• output of partial threads in PDB format
• cleaning of partial threads based on TM-score [2]
• multithreading

External packages/libraries:

• kdtree library by John Tsiombikas
• C++ TM-align routine from Yang Zhang lab

References

[1] S Ovchinnikov et al. Protein Structure Determination using Metagenome sequence data. (2017) Science. 355(6322):294–8.

[2] Y Zhang & J Skolnick. TM-align: a protein structure alignment algorithm based on the TM-score. (2005) Nucleic Acids Res. 33(7):2302-9.