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

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 beta and gamma). We have previously described an atypical plant gamma-subunit, AKINbetagamma, which contains an N-terminal tail similar to the so-called KIS domain normally present in beta-subunits. However, it is not known whether AKINbetagamma 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 AKINbetagamma is an integral component of active SnRK1 complexes in plant cells. Using complementary methodological approaches, we also show that AKINbetagamma associates through homomeric interactions mediated by both, the gamma- and, unexpectedly, the KIS/CBM domain.