InterPro domain: IPR037170

This family represents the regulatory beta-1 subunit of the plant SNF1-related protein kinase (SnRK) complex, probably a trimeric complex consisting of an alpha catalytic subunit, and a beta and a gamma non-catalytic regulatory subunits [ 1 ]. In Arabidopsis, there are two isoforms of the catalytic subunit (AKIN10 and AKIN11), three beta subunits (AKINbeta1, AKINbeta2, and AKINbeta3) and one gamma subunit (AKINg) [ 2 , 3 ]. The SnRK complex in higher plants plays a role in signal transduction cascades regulating gene expression, carbohydrate and nitrogen metabolism [ 4 ]. Some known SnRK1 substrates are key metabolic enzymes such as sucrose phosphate synthase, nitrate reductase, and HMG-CoA reductase [ 5 ], while others are transcription factors [ 6 ]. Its physical interaction with nitrate reductase specifically occurs via the AKINbeta1 subunit [ 7 ].

Beta subunits show conserved domains in different organisms. These domains include the Association with the SNF1 Complex (ASC) domain, which is important for interaction with the alpha and gamma subunits, and a specialised carbohydrate-binding module named the Glycogen Binding Domain (GBD). In Arabidopsis, only AKINbeta1 and AKINbeta2 exhibit both the GBD and the ASC domains [ 7 , 7 ]. AKINbeta3 could be a plant specific subunit [ 7 ].

1. Arabidopsis thaliana proteins related to the yeast SIP and SNF4 interact with AKINalpha1, an SNF1-like protein kinase. Plant J. 18, 541-50
2. Beta-subunits of the SnRK1 complexes share a common ancestral function together with expression and function specificities; physical interaction with nitrate reductase specifically occurs via AKINbeta1-subunit. Plant Physiol. 148, 1570-82
3. Structural and functional basis for starch binding in the SnRK1 subunits AKINβ2 and AKINβγ. Front Plant Sci 5, 199
4. AKINbeta1 is involved in the regulation of nitrogen metabolism and sugar signaling in Arabidopsis. J Integr Plant Biol 51, 513-20
5. Metabolic signalling and carbon partitioning: role of Snf1-related (SnRK1) protein kinase. J. Exp. Bot. 54, 467-75
6. AKIN10 and FUSCA3 interact to control lateral organ development and phase transitions in Arabidopsis. Plant J. 69, 809-21
7. AKINbeta3, a plant specific SnRK1 protein, is lacking domains present in yeast and mammals non-catalytic beta-subunits. Plant Mol. Biol. 56, 747-59