PRotein Ontology (PRO) Release 59.0 (23-Sep-2019)

There are 217177 PRO terms in the Protein Ontology. Those representing individual proteins are mapped to 139078 UniProtKB sequences.
      517 terms are in the 'family' category.
    23478 terms are in the 'gene' category.
     8030 terms are in the 'sequence' category.
     4964 terms are in the 'modification' category.
      211 terms are in the 'complex' category.
       31 terms are in the 'organism-family' category.
    99431 terms are in the 'organism-gene' category.
       27 terms are in the 'organism-genegroup' category.
      154 terms are in the 'organism-seqgroup' category.
    70747 terms are in the 'organism-sequence' category.
     6658 terms are in the 'organism-modification' category.
      421 terms are in the 'organism-complex' category.
       25 terms are in the 'union' category.
       72 terms are in the 'external' category.
 2596 terms have some kind of annotation, codifying the information from 1657 papers.
     4442 connections to GO (1724 PRO terms).
      616 connections to Pfam (369 PRO terms).
       27 connections to SO (24 PRO terms).
      611 annotations of a phenotype (586 PRO terms).

The ontology includes a subset of terms from other ontologies and resources that are used for logical definitions.

_Current changes_

1) A new synonym type "Gene-based" has been added. These are intended to indicate synonyms that are based on gene symbols or ordered locus names. Such synonyms, because they designate genes and not proteins, are not considered EXACT. Nonetheless, because they are often used to refer to proteins as well, the new synonym type will help distinguish these from non-EXACT synonyms that actually do refer to proteins. 
2) The FTP site has been discontinued. All downloads (past and current) will be accessible using http and the appropriate PURLs.
3) We have added a new download option for the large reasoned OWL file: pro_reasoned.owl.gz accessible using the PURL http://www.obolibrary.org/obo/pr.owl.gz

_Forthcoming changes_

1) A new synonym type "PRO-org-label" will be added to appropriate terms. Currently the PRO-short-label synonyms use an orthology-based mechanism to identify related terms across species. The new synonym type will identify related terms based on the gene name in the given organism.