Identification of iron-regulated outer membrane proteins in uropathogenic Proteus mirabilis and its relationship with heme uptake.

The effect of iron deprivation on the expression of outer membrane proteins and the ability to use heme as an iron source by uropathogenic Proteus mirabilis, Pr 6515, was studied. Examination of iron-restricted bacteria showed three outer membrane proteins ranging from 66 to 75 kDa to be affected by iron restriction, as well as a newly expressed 64-kDa protein. These proteins were induced within 15 minutes of iron-deprivation. The strain grew in the presence of ferric citrate, hemin and hemoglobin as iron sources, but could not use transferrin, lactoferrin or siderophores from exogenous sources. The 64- and 66-kDa proteins showed hemin-binding activity by affinity chromatography, and both reacted in Western blots with sera from mice transurethrally infected with the same strain. We suggest that P. mirabilis expresses iron-regulated outer membrane proteins that could be involved in heme uptake and may have a role in pathogenesis.