School of Pharmacy, Anhui University of Chinese Medicine, Hefei, China.
College of Life Science, Capital Normal University, Beijing, China.
Plant Signal Behav. 2022 Dec 31;17(1):2005881. doi: 10.1080/15592324.2021.2005881. Epub 2021 Nov 23.
The IRON-REGULATED TRANSPORTER1 (IRT1) is critical for iron uptake in roots, and its exocytosis to the plasma membrane (PM) is regulated by detergent-resistant membranes. However, studies on IRT1 exocytosis and function in response to iron status are limited. Presently, we found that the histidine-rich motif (HRM) of MxIRT1 could bind to iron directly and HRM determined the delivery of MxIRT1 to the PM, after which the cholesterol recognition amino acid consensus (CRAC) motif-regulated MxIRT1 mediated metal transport. IMAC assay revealed that H192 was the vital site for HRM binding to Fe, and metal-binding activity was stopped after the deletion of HRM (MxIRT1∆HM) or in H192 site-directed mutants (HA). MxIRT1∆HM or HA in transgenic yeast and Arabidopsis failed to localize in the PM and displayed impaired iron absorption. In the PM, Y266 in CRAC was required for metal transport; Y266A transgenic Arabidopsis displayed the same root length, Cd flux, and Fe concentration as Arabidopsis mutant under iron-deficient conditions. Therefore, H192 in HRM may be an iron sensor to regulate delivery of MxIRT1 vesicles to the PM after binding with iron; Y266 in CRAC acts as an iron sensor for active metal transport under iron-deficient conditions.
铁调节转运蛋白 1（IRT1）对于根吸收铁至关重要，其质膜（PM）外排受去污剂抗性膜调节。然而，IRT1 外排及其对铁状态响应的功能研究有限。目前，我们发现 MxIRT1 的组氨酸丰富基序（HRM）可以直接与铁结合，并且 HRM 决定了 MxIRT1 向 PM 的递呈，之后胆固醇识别氨基酸共识（CRAC）基序调节的 MxIRT1 介导金属转运。IMAC 分析表明 H192 是 HRM 与 Fe 结合的关键位点，并且在缺失 HRM（MxIRT1∆HM）或 H192 定点突变（HA）后，金属结合活性停止。MxIRT1∆HM 或 HA 在转基因酵母和拟南芥中无法定位于 PM 并表现出铁吸收受损。在 PM 中，CRAC 中的 Y266 对于金属转运是必需的；Y266A 转基因拟南芥在缺铁条件下显示出与拟南芥突变体相同的根长、Cd 通量和 Fe 浓度。因此，HRM 中的 H192 可能是一种铁传感器，用于在与铁结合后调节 MxIRT1 囊泡向 PM 的递呈；CRAC 中的 Y266 在缺铁条件下作为活性金属转运的铁传感器发挥作用。
