Complex portal: a resource for functionally annotated macromolecular complexes

The Complex Portal is a manually curated encyclopaedic resource of macromolecular complexes from 28 species which includes over 2150 human complexes. The resource enables the linking of knowledge on protein complexes across multiple databases, providing a reference set of component molecules with stable, versioned accession numbers. The Complex Portal defines a macromolecular complex as a stable set of (two or more) interacting protein and/or RNA molecules which can be co-purified and have been shown to exist as a functional unit in vivo. The degree of evidence for a complex is defined using the Evidence and Conclusion Ontology (ECO). Complexes are curated to a high level of granularity to include details on isoforms, variants, stoichiometry, and tissue-specificity. The Complex Portal is an active collaborator in the UniPlex project, a collaborative effort to expand the database and map the human complexome based on HuMap3.0 (http://proteincomplexes.org/) and Proteome HD 2.0 (https://www.proteomehd.net/). The newly generated data will be incorporated into the Complex Portal and regularly updated. The data derived will be consolidated from a combination of machine-learning predicted complexes and protein co-expression data, and further validated by manual curation. Data generated by the UniPlex project will greatly enrich the database, allowing for further exploration of the role of complexes through IntAct"s Cytoscape application using GO enrichment tags and disease ontology terms. The project will also enable the comparison of complexes under diverse cellular conditions for a better understanding of their role in biological functions and processes. The data in the Complex Portal is freely available and can be downloaded in PSI-MI XML, MI-JSON and tab-delimited formats (https://www.ebi.ac.uk/complexportal/download).