title: Reuse of structural domain-domain interactions in protein networks.
abstract: BACKGROUND
  Protein interactions are thought to be largely mediated by interactions between structural domains. Databases such as iPfam relate interactions in protein structures to known domain families. Here, we investigate how the domain interactions from the iPfam database are distributed in protein interactions taken from the HPRD, MPact, BioGRID, DIP and IntAct databases.
  
  
  RESULTS
  We find that known structural domain interactions can only explain a subset of 4-19% of the available protein interactions, nevertheless this fraction is still significantly bigger than expected by chance. There is a correlation between the frequency of a domain interaction and the connectivity of the proteins it occurs in. Furthermore, a large proportion of protein interactions can be attributed to a small number of domain interactions. We conclude that many, but not all, domain interactions constitute reusable modules of molecular recognition. A substantial proportion of domain interactions are conserved between E. coli, S. cerevisiae and H. sapiens. These domains are related to essential cellular functions, suggesting that many domain interactions were already present in the last universal common ancestor.
  
  
  CONCLUSIONS
  Our results support the concept of domain interactions as reusable, conserved building blocks of protein interactions, but also highlight the limitations currently imposed by the small number of available protein structures.
authors.affiliation: Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, UK. bsb@sanger.ac.uk
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schuster-Böckler
authors.forename: Alex
authors.initials: A
authors.lastname: Bateman
mesh_terms: D030562:Databases, Protein; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D019143:Evolution, Molecular; D006801:Humans; D008957:Models, Genetic; D025941:Protein Interaction Mapping / Q000379:methods*; D017434:Protein Structure, Tertiary; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D012984:Software; D013045:Species Specificity
chemical_list: D029968:Escherichia coli Proteins; D029701:Saccharomyces cerevisiae Proteins