Involved in the regulation of nitrogen metabolism (PubMed:11807063). Regulates the activity of its targets by protein-protein interaction in response to the nitrogen status of the cell (PubMed:15752204, PubMed:15824904). Allows finetuning control of the glutamine synthetase GlnA1 under changing nitrogen availabilities via direct protein interaction (PubMed:15752204). Inhibitory effects on GlnA1 are abolished in the presence of the effector 2-oxoglutarate. Homotrimer (PubMed:11807063). Interacts and forms stable complexes with the glutamine synthetase GlnA1 (PubMed:15752204). Expressed under nitrogen-limiting conditions. Disruption mutant exhibits a partial growth defect under nitrogen limitation when molecular nitrogen is used as the sole nitrogen source. Unlike the enteric GlnK proteins, Glnk1 is not covalently modified by uridylylation under nitrogen limitation. Belongs to the P(II) protein family.