Adenine nucleotides-binding subunit gamma of AMP-activated protein kinase (AMPK), an energy sensor protein kinase that plays a key role in regulating cellular energy metabolism. In response to reduction of intracellular ATP levels, AMPK activates energy-producing pathways and inhibits energy-consuming processes: inhibits protein, carbohydrate and lipid biosynthesis, as well as cell growth and proliferation. AMPK acts via direct phosphorylation of metabolic enzymes, and by longer-term effects via phosphorylation of transcription regulators. Gamma non-catalytic subunit mediates binding to AMP, ADP and ATP, leading to activate or inhibit AMPK: AMP-binding results in allosteric activation of alpha catalytic subunit (ssp2) both by inducing phosphorylation and preventing dephosphorylation of catalytic subunits. AMPK is a heterotrimer of an alpha catalytic subunit (ssp2), a beta (amk2) and a gamma non-catalytic subunits (cbs2). Forms a dimer of trimers. The 4 CBS domains mediate binding to nucleotides. Of the 4 potential nucleotide-binding sites, 2 are occupied, designated as sites 2 (or A), and 3 (or B) based on the CBS modules that provide the acidic residue for coordination with the 2'- and 3'-hydroxyl groups of the ribose of AMP. Site 3 can bind either AMP, ADP or ATP (AMP, ADP or ATP 2). Site 2 binds specifically ADP (ADP 1) and is likely to be responsible for protection of a conserved threonine in the activation loop of the alpha catalytic subunit through conformational changes induced by binding of ADP. Belongs to the 5'-AMP-activated protein kinase gamma subunit family.