Protein phosphorylation is a post-translational modification that regulates an astonishing number of critical biological processes in multicellular organisms. Cellular protein phosphorylation is an enormously complex dynamic system: over 510 distinct protein kinases and 100 phosphoprotein phosphatases are encoded in the human genome, and upwards of 40% of cellular proteins may be phosphorylated during some stage of growth and differentiation. Many proteins are multiply phosphorylated on scores of sites, making it likely that there are minimally 100,000 distinct phosphorylation sites in the mammalian proteome. It is the intention of the scientists who are designing and implementing PhosphoSite to provide an accurate and comprehensive source of information about mammalian protein phosphorylation sites. Our goal is to identify and organize information about all in vivo phosphorylation sites in human and mouse proteomes and to provide information and resources that will facilitate phosphorylation research. PhosphoSite is a curated, sequence-oriented protein database dedicated to in vivo phosphorylation sites. Information in PhosphoSite version 1.0 includes: (a) The phosphorylated residue and its surrounding sequence. We consider this information to be the central, organizing feature of PhosphoSite. (b) Orthologous sites in other species; this should assist investigators in determining if a phosphorylation site in species A might also be phosphorylated in species B. (c) The location within domains and motifs; this should assist investigators in inferring possible biological functions of phosphorylation sites. (d) Links to other online resources including the Alliance for Cell Signaling, the Protein Kinase Resource, and Scansite. Scansite predicts likely sites for protein phosphorylation by particular kinases and likely sites for interaction with other signaling proteins. This information, based upon vitro data, will be highly complimentary to that provided by PhosphoSite. (e) Literature references which demonstrate the in vivo nature and significance of the phosphorylation site. (...) Curated information will come from literature reports as well as from high-throughput phosphosite discovery programs. Information extracted from the public domain will be freely available for educational users. Proprietary information from phosphorylation site discovery programs may be available on a subscription basis. Corporations will need to pay a reasonable yearly fee to legally access PhosphoSite. ... [Information of the supplier, modified]
