Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms

Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms Nature 555, 7697 (2018). doi:10.1038/nature25982 Authors: Jeffrey B. McQuaid, Adam B. Kustka, Miroslav Oborník, Aleš Horák, John P. McCrow, Bogumil J. Karas, Hong Zheng, Theodor Kindeberg, Andreas J. Andersson, Katherine A. Barbeau & Andrew E. Allen In vast areas of the ocean, the scarcity of iron controls the growth and productivity of phytoplankton. Although most dissolved iron in the marine environment is complexed with organic molecules, picomolar amounts of labile inorganic iron species (labile iron) are maintained within the euphotic zone and serve as an important source of iron for eukaryotic phytoplankton and particularly for diatoms. Genome-enabled studies of labile iron utilization by diatoms have previously revealed novel iron-responsive transcripts, including the ferric iron-concentrating protein ISIP2A, but the mechanism behind the acquisition of picomolar labile iron remains unknown. Here we show that ISIP2A is a phytotransferrin that independently and convergently evolved carbonate ion-coordinated ferric iron binding. Deletion of ISIP2A disrupts high-affinity iron uptake in the diatom Phaeodactylum tricornutum, and uptake is restored by complementation with human transferrin. ISIP2A is internalized by endocytosis, and manipulation of the seawater carbonic acid system reveals a second-order dependence on the concentrations of labile iron and carbo...
Source: Nature - Category: Research Authors: Tags: Letter Source Type: research