Coordinate regulation by iron of the synthesis of phenolate compounds and three outer membrane proteins in Escherichia coli

Abstract

The biosynthesis of the low-molecular-weight iron carrier enterochelin and of three outer membrane polypeptides appears to be coordinately regulated by the amount of cell-associated iron in Escherichia coli K-12. Measurements of iron acquisition made throughout the growth cycle in iron-deficient media indicate that a very rapid accumulation of iron occurs in the first 2 h of growth; there is comparatively little iron uptake during exponential growth, which results in a gradual decrease in the cellular iron content with each generation. When this level falls below 400 ng of iron per mg (dry weight) of cells, there is a simultaneous onset of synthesis of the three outer membrane polypeptides and of enterochelin. This coordinate regulation was also observed in cells able to transport iron actively using only citrate as an iron-carrier.

Effect of iron concentration and growth rate on the expression of protein G in Pseudomonas aeruginosa

“…The IRMPs of Escherichia cob behave similarly [17] as expected for proteins associated with highaffinity iron uptake systems. It is conceivable that protein G comprises part of a low-affinity iron uptake system, which is repressed and superseded by the high molecular weight IRMPs of the high Fig.…”

The outer membrane proteins of the fish pathogens Aeromonas hydrophila, Aeromonas salmonicida and Edwardsiella tarda

“…Iron-binding proteins induced under iron limiting conditions have been reported in V. anguillarum strains [16] and in E. coli [17]. 3 New proteins in the outer membrane of E. tarda were induced under limiting levels of iron.…”

Role of siderophore in iron uptake in cowpea Rhizobium GN1 (peanut isolate): Possible involvement of iron repressible outer membrane proteins

“…Since these proteins are not synthesized under Fe-sufficient conditions, it is possible that one of these proteins constitute siderophore receptor protein. This may explain siderophore-mediated enhanced iron uptake only in iron-starved ceils and not in iron-sufficient cells, in Escherichia coli the outer membrane receptor protein (Fep A) for enterobactin has been reported to be of molecular mass of 81 kDa [9]. Similarly, in Pseudomonas aeruginosa, an 80 kDa iron-regulated outer membrane polypep-188 tide has been shown to be a receptor for the Fe-Pyoverdin complex [8].…”

“…In Gram-negative bacteria, in addition to the production of siderophores, iron deficiency is also characterized by the appearance of one or more new major proteins in the outer membranes termed iron regulated outer membrane proteins (IROMPs) [7]. In some cases IROMPs have been shown to be Fe-siderophore receptors [8,9].…”