Cardarelli, LiaSaak, ChristinaGibbs, Karine2015-07-132015Cardarelli, Lia, Christina Saak, and Karine A. Gibbs. 2015. “Two Proteins Form a Heteromeric Bacterial Self-Recognition Complex in Which Variable Subdomains Determine Allele-Restricted Binding.” mBio 6 (3): e00251-15. doi:10.1128/mBio.00251-15. http://dx.doi.org/10.1128/mBio.00251-15.2150-7511http://nrs.harvard.edu/urn-3:HUL.InstRepos:17295588ABSTRACT Self- versus nonself-recognition in bacteria has been described recently through genetic analyses in multiple systems; however, understanding of the biochemical properties and mechanisms of recognition-determinant proteins remains limited. Here we extend the molecular and biochemical understanding of two recognition-determinant proteins in bacteria. We have found that a heterotypic complex is formed between two bacterial self-recognition proteins, IdsD and IdsE, the genes of which have been shown to genetically encode the determinants for strain-specific identity in the opportunistic bacterial pathogen Proteus mirabilis. This IdsD-IdsE complex forms independently of other P. mirabilis-encoded self-recognition proteins. We have also shown that the binding between IdsD and IdsE is strain- and allele-specific. The specificity for interactions is encoded within a predicted membrane-spanning subdomain within each protein that contains stretches of unique amino acids in each P. mirabilis variant. Finally, we have demonstrated that this in vitro IdsD-IdsE binding interaction correlates to in vivo population identity, suggesting that the binding interactions between IdsD and IdsE are part of a cellular pathway that underpins self-recognition behavior in P. mirabilis and drives bacterial population sociality.en-USJournal Article2015-07-1310.1128/mBio.00251-15