title: Nature of the protein universe.
abstract: The protein universe is the set of all proteins of all organisms. Here, all currently known sequences are analyzed in terms of families that have single-domain or multidomain architectures and whether they have a known three-dimensional structure. Growth of new single-domain families is very slow: Almost all growth comes from new multidomain architectures that are combinations of domains characterized by approximately 15,000 sequence profiles. Single-domain families are mostly shared by the major groups of organisms, whereas multidomain architectures are specific and account for species diversity. There are known structures for a quarter of the single-domain families, and >70% of all sequences can be partially modeled thanks to their membership in these families.
authors.affiliation: Department of Structural Biology, Stanford University, Stanford, CA 94305-5126, USA. michael.levitt@stanford.edu
authors.forename: Michael
authors.initials: M
authors.lastname: Levitt
mesh_terms: D000595:Amino Acid Sequence; D030562:Databases, Protein; D019143:Evolution, Molecular; D008958:Models, Molecular; D005810:Multigene Family; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D040681:Structural Homology, Protein
chemical_list: D011506:Proteins