Fig 9. Protein complexes are rich in highly-conserved proteins of unknown function.

(A) The list of EcoCyc E. coli protein complexes was compared on the basis of component presence vs. absence across seven other species in this study. Conserved complexes, in this figure, are those in which at least one orthologous component is present in the target species. Similarly, essential complexes include at least one component found to be essential in both E. coli and in the target species. (B) As in (A), but within the subset of EcoCyc complexes containing at least one protein of unknown or unclear function. In these instances, the complex itself may have a known function though the roles of its components may remain unclear. (C) Examples of experimentally-observed protein complexes containing proteins of unknown function. E. coli complex examples from Hu et al. are shown at left, M. pneumoniae complexes from Kühner et al. are shown at right. Complexes are labeled with the identifier used in their corresponding study.