Maize AKINβγ dimerizes through the KIS/CBM domain and assembles into SnRK1 complexes

Abstract

The SNF1/AMPK/SnRK1 complex is an intracellular energy sensor composed of three types of subunits: the SnRK1 kinase and two regulatory, non-catalytic subunits (designated b and c). We have previously described an atypical plant c-subunit, AKINbc, which contains an N-terminal tail similar to the so-called KIS domain normally present in b-subunits. However, it is not known whether AKINbc normally associates with endogenous SnRK1 complexes in vivo, nor how its unique domain structure might contribute to SnRK1 function. Here, we present evidence that maize AKINbc is an integral component of active SnRK1 complexes in plant cells. Using complementary methodological approaches, we also show that AKINbc associates through homomeric interactions mediated by both, the c- and, unexpectedly, the KIS/CBM domain.