Inositol polyphosphate-mediated iron transport in Pseudomonas aeruginosa

It has previously been shown that myo-inositol hexakisphosphate (myo-InsP(6 )) mediates iron transport into Pseudomonas aeruginosa and overcomes iron-d ependent growth inhibition. In this study, the iron transport: properties o f myo-inositol trisphosphate and tetrakisphosphate regio-isomers were studi ed. Pseudomonas aeruginosa accumulated iron (III) at similar rates whether complexed with myo-Ins(1,2,3)P-3 or myo-InsP(6). Iron accumulation from oth er compounds, notably D/L myo-Ins(1,2,4,5)P-4 and another inositol trisphos phate regio-isomer, D-myo-Ins(1,4,5)P-3, was dramatically increased. Iron t ransport profiles from myo-InsP(6) into mutants lacking the outer membrane porins oprF, oprD and oprP were similar to the wild-type, indicating that t hese porins are not involved in the transport process. The rates of reducti on of iron (III) to iron (II) complexed to any of the compounds by a Ps. ae ruginosa cell lysate were similar, suggesting that a reductive mechanism is not the rate-determining step.