Shigella Iron Transport Systems
A. R. Mey, E. E. Wyckoff and S. M. Payne
from: Shigella: Molecular and Cellular Biology (Edited by: William D. Picking and Wendy L. Picking). Caister Academic Press, U.K. (2016) Pages: 27-48.
Shigella species have several different transport systems for acquisition of the essential element iron. These include both ferric and ferrous iron transporters. These pathogens synthesize and secrete siderophores, high-affinity ferric iron chelators, and both catechol and hydroxamate siderophores have been identified in Shigella. Additionally, the Shigella species have transporters for free ferric (Sit) and ferrous (Feo) iron, and Shigella dysenteriae has an outer membrane receptor and transport system for heme. The expression of genes encoding these transporters is regulated by environmental cues including iron, oxygen and temperature. Iron regulation is accomplished by Fur, a transcriptional regulator that represses these genes in the presence of iron. FNR and ArcAB regulate expression of the genes in response to oxygen levels, while temperature controls expression of the heme transporter ShuA post-transcriptionally through formation of a FourU thermometer structure in the mRNA. Thus, Shigella are able to adapt to a variety of different environments and different iron sources to obtain sufficient iron for growth. In aerobic, iron-limiting conditions in vitro, expression of siderophores allows maximal growth, while the Sit system is crucial to replication in the intracellular environment of the host epithelium read more ...