title: Siderophore-mediated cargo delivery to the cytoplasm of Escherichia coli and Pseudomonas aeruginosa: syntheses of monofunctionalized enterobactin scaffolds and evaluation of enterobactin-cargo conjugate uptake.
abstract: The design and syntheses of monofunctionalized enterobactin (Ent, L- and D-isomers) scaffolds where one catecholate moiety of enterobactin houses an alkene, aldehyde, or carboxylic acid at the C5 position are described. These molecules are key precursors to a family of 10 enterobactin-cargo conjugates presented in this work, which were designed to probe the extent to which the Gram-negative ferric enterobactin uptake and processing machinery recognizes, transports, and utilizes derivatized enterobactin scaffolds. A series of growth recovery assays employing enterobactin-deficient E. coli ATCC 33475 (ent-) revealed that six conjugates based on L-Ent having relatively small cargos promoted E. coli growth under iron-limiting conditions whereas negligible-to-no growth recovery was observed for four conjugates with relatively large cargos. No growth recovery was observed for the enterobactin receptor-deficient strain of E. coli H1187 (fepA-) or the enterobactin esterase-deficient derivative of E. coli K-12 JW0576 (fes-), or when the D-isomer of enterobactin was employed. These results demonstrate that the E. coli ferric enterobactin transport machinery identifies and delivers select cargo-modified scaffolds to the E. coli cytoplasm. Pseudomonas aeruginosa PAO1 K648 (pvd-, pch-) exhibited greater promiscuity than that of E. coli for the uptake and utilization of the enterobactin-cargo conjugates, and growth promotion was observed for eight conjugates under iron-limiting conditions. Enterobactin may be utilized for delivering molecular cargos via its transport machinery to the cytoplasm of E. coli and P. aeruginosa thereby providing a means to overcome the Gram-negative outer membrane permeability barrier.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Tengfei
authors.initials: T
authors.lastname: Zheng
authors.forename: Justin L
authors.initials: JL
authors.lastname: Bullock
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Nolan
mesh_terms: D001692:Biological Transport; D004758:Enterobactin / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000382:microbiology; D006801:Humans; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D017262:Siderophores / Q000737:chemistry / Q000378:metabolism*
chemical_list: D017262:Siderophores; D004758:Enterobactin