Introduction
PiQSi is a community effort that facilitates the investigation and curation of quaternary structures. Given a PDB identifier or a protein sequence, it displays information about the quaternary structure of homologous proteins on a single web-page. This information allows a quick comparison of the quaternary structure(s) of the members of a protein family. So far, the web-server has allowed the manual curation of ~15000 structures of PDB Biological Units, of which about 15% were found to be likely errors (e.g. guilty).
NEW Several features have been added in this new release!
- Like in 3D Complex, you can roll over a graph node to search homologues (i) by complex, (ii) by polypeptide chain, or (iii) by domain:
- You can now view or download a structure by clicking on the "R" link ("R" is for Rasmol).
- We started a project that consists of the curation of human/yeast/coli proteins.
- A score, which reflects the probability for a protein to be "guilty", enables one to curate likely errors first.
- You can have a look at the "pick of the day", curate it, and enter the new Wall of Fame :)
Please, register and participate to the quaternary state annotation of PDB structures!
If you would like to refer to PiQSi, please cite:
Levy ED. PiQSi: protein quaternary structure investigation. Structure. 2007 Nov;15(11):1364-7 - Pubmed
Pick of the day - is this protein correct?
This protein is likely to have a wrong quaternary structure because: (i) it does not form a closed symmetry (see help for details on symmetry), and (ii) it shares 92% sequence identity with a symmetric dimer. You can contribute to PiQSi by looking at the paper and annotating the quaternary state :
| Code | Pic | Error? | Sym1 | Nsub1 | Sym2 | Nsub2 | SProt | Weight | Ref | H | E | R | Org | Fun | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PDB | PiQSi | ||||||||||||||
| 3gkt_1 |  | ? | NPS | 1 | ? | ? | Q9ER97 | P | H | E | R | Mus musculus | OXYGEN STORAGE/TRANSPORT PROTEIN | ||
Illustration of PiQSi information
Each protein can be displayed along with its homologs of known structure, and information that helps to determine the biological
oligomeric state.
