Structural and functional properties of a plant NRAMP-related aluminum transporter
Karthik Ramanadane, Márton Liziczai, Dragana Markovic, Straub MS, Gian Tizio Rosalen, Anto Udovcic, Raimund Dutzler, Cristina Manatschal
Abstract
The transport of transition metal ions by members of the SLC11/NRAMP family constitutes a ubiquitous mechanism for the uptake of Fe 2+ and Mn 2+ across all kingdoms of life. Despite the strong conservation of the family, two of its branches have evolved a distinct substrate preference with one mediating Mg 2+ uptake in prokaryotes and another the transport of Al 3+ into plant cells. Our previous work on the SLC11 transporter from Eggerthella lenta revealed the basis for its Mg 2+ selectivity (Ramanadane et al., 2022). Here, we have addressed the structural and functional properties of a putative Al 3+ transporter from Setaria italica . We show that the protein transports diverse divalent metal ions and binds the trivalent ions Al 3+ and Ga 3+ , which are both presumable substrates. Its cryo-electron microscopy (cryo-EM) structure displays an occluded conformation that is closer to an inward- than an outward-facing state, with a binding site that is remodeled to accommodate the increased charge density of its transported substrate.