475 / 2019-02-27 22:13:19

Calcium-promoted interaction between peripheral membrane protein EHB1 and metal transporter IRT1 inhibits Arabidopsis iron acquisition

iron acquisition, IRT1, EHB1, protein-protein interaction, calcium-dependent interaction

全体主题 > Abiotic Stress

Being a key transition element employed in the biosphere, iron is crucial for the operation of living organisms, however its cellular excess can be deleterious. Maintaining the fine balance of optimal iron availability in Arabidopsis requires the precise operation of iron import through the principal iron transporter, IRON-REGULATED TRANSPORTER1 (IRT1). Targeted inhibition of IRT1 can be of critical importance for prevention of oxidative stress and promoting plant survival. Here, we report the identification of an IRT1 inhibitor, the peripheral membrane protein ENHANCED BENDING1 (EHB1). EHB1 interacts with the cytoplasmically-exposed variable region of IRT1. We show that this interaction is greatly promoted by the presence of calcium. We found that EHB1 binds lipids characteristic for the plasma membrane, and the interaction between EHB1 and plant membranes is calcium-dependent. Molecular simulations show the EHB1 membrane binding to be a two-step process preceding an interaction between EHB1 and IRT1. Genetic and physiological analyses show that EHB1 acts as a negative regulator of iron acquisition. The presence of EHB1 prevents the IRT1-mediated complementation of iron-deficient fet3fet4 yeast. The data suggests that EHB1 acts as a direct inhibitor of IRT1-mediated iron import into the cell. Our finding represents a major step in understanding plant iron acquisition, a process which underlies the primary production of bioavailable iron for land ecosystems.