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The hybrid Four‐ CBS ‐Domain KIN βγ subunit functions as the canonical γ subunit of the plant energy sensor Sn RK 1
Author(s) -
Ramon Matthew,
Ruelens Philip,
Li Yi,
Sheen Jen,
Geuten Koen,
Rolland Filip
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12192
Subject(s) - heterotrimeric g protein , protein subunit , bimolecular fluorescence complementation , biology , arabidopsis , cyclic nucleotide binding domain , microbiology and biotechnology , ampk , biochemistry , gene , g protein , phosphorylation , mutant , protein kinase a , peptide sequence , signal transduction
Summary The AMPK/SNF1/SnRK1 protein kinases are a family of ancient and highly conserved eukaryotic energy sensors that function as heterotrimeric complexes. These typically comprise catalytic α subunits and regulatory β and γ subunits, the latter function as the energy‐sensing modules of animal AMPK through adenosine nucleotide binding. The ability to monitor accurately and adapt to changing environmental conditions and energy supply is essential for optimal plant growth and survival, but mechanistic insight in the plant Sn RK 1 function is still limited. In addition to a family of γ‐like proteins, plants also encode a hybrid βγ protein that combines the Four‐Cystathionine β‐synthase ( CBS )‐domain ( FCD ) structure in γ subunits with a glycogen‐binding domain ( GBD ), typically found in β subunits. We used integrated functional analyses by ectopic Sn RK 1 complex reconstitution, yeast mutant complementation, in‐depth phylogenetic reconstruction, and a seedling starvation assay to show that only the hybrid KIN βγ protein that recruited the GBD around the emergence of the green chloroplast‐containing plants, acts as the canonical γ subunit required for heterotrimeric complex formation. Mutagenesis and truncation analysis further show that complex interaction in plant cells and γ subunit function in yeast depend on both a highly conserved FCD and a pre‐ CBS domain, but not the GBD . In addition to novel insight into canonical AMPK / SNF /Sn RK 1 γ subunit function, regulation and evolution, we provide a new classification of plant FCD genes as a convenient and reliable tool to predict regulatory partners for the Sn RK 1 energy sensor and novel FCD gene functions.