Arabidopsis KIN gamma subunit 1 has a potential to regulate activity of sucrose nonfermenting 1-related protein kinase 2s (SnRK2s) in vitro

Abstract

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</p><p>To respond to environmental changes promptly, plants must regulate their signalling pathways with precision. <em>Sucrose</em><i> </i>non fermenting1 (SNF1)-related protein kinases (SnRK) 2 are essential kinases in abiotic stress responses, including responses to abscisic acid (ABA). Although homologs of SnRKs in yeast require a γ-subunit for full activation, it has been unclear whether SnRK2s are affected by γ-subunits. In this report, we aimed to show the effect of <i>Arabidopsis</i> KIN gamma subunit 1 (KING1), which is a potential γ-subunit, on the activity of SnRK2. Recombinant KING1 bound to SnRK2.6 (a.k.a. OST1) and functionally inhibited its activity <i>in vitro</i>. On the other hand, KING1 facilitated the activity of SnRK2.2. Structural models suggest that significant structural changes occur as a result of KING1 binding to the C-terminal tail of SnRK2s. Since KING1 inhibits the kinase activity of a chimeric protein consisting of the N-terminal domain of SnRK2.6 and the C-terminal domain of SnRK2.2, the regulation by KING1 is determined by N-terminal domain of SnRK2s. Together, these results show that KING1 can mediate activity of SnRK2s <i>in vitro</i>.</p>