Images and cellular experiments reveal how the plant transporter AMT1;1 is regulated on both sides of the cell membrane. An extracellular bond supports its structure, while a modification on the intracellular side inhibits transport. The peer-reviewed study in Arabidopsis thaliana connects molecular shape with nutrient movement, but leaves the exact chemical species crossing the membrane unresolved and measures no field yield benefit.
The protein AMT1;1 transports ammonium across cell membranes in Arabidopsis thaliana, a plant species. Researchers used cryo-electron microscopy to examine its structure in different states, then combined the images with biochemical experiments, mutations and molecular-dynamics simulations. The peer-reviewed study follows a transporter made of three subunits, each with a membrane-spanning core and regulatory regions on either side.[1]
In yeast deficient in ammonium transport, expressing the plant protein partly restored growth under low-ammonium conditions. Another cellular experiment measured stable-isotope-labelled ammonium accumulation and compared transporter-expressing cells with empty-vector controls. The resulting apparent Km was 49.53 ± 9.47 micromolar, supporting high-affinity transport. The accumulation measurements were repeated independently three times.[1]
An extracellular disulfide bond helped maintain stable subunit assembly and transport activity. Removing the region or changing a participating cysteine reduced both. The structure lost stability under reducing conditions. Low-level oxidation applied afterwards partly restored structural populations. On the intracellular side, a modification mimicking phosphorylation changed regulatory contacts and inhibited transport.[1]
The images show the transport route across the membrane, connecting its outer entrance with its inner exit. Whether ammonium loses a proton and precisely which chemical species crosses the membrane remain unresolved. The experiments concern molecular transport and regulation; field nitrogen-use efficiency and crop yields were not directly measured.[1]
