Summary: Ferrichrome-promoted iron uptake in k12 is strictly dependent upon the gene product, a “minor” outer membrane protein. By selection for mutants of resistant to phages which require “major” outer membrane proteins as receptors, strains with pronounced protein deficiencies were constructed. Such strains were tested for anomalous behaviour of ferrichrome transport. No significant differences in iron uptake were detected in 12 strains with markedly reduced amounts of protein I. However, a reduction in the initial velocity (up to 40%) was observed in deficient in outer membrane protein II. This difference was only evident when cells were grown under iron-starvation conditions; it was abolished when cells were grown in rich medium. Kinetic parameters for ferrichrome transport were determined for maximum velocity but not for ; double reciprocal plots showed a biphasic nature, probably attributable to a limited number of outer membrane binding sites and to the multi-component nature of the ferrichrome-iron transport system.


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