Nitrogen is an essential component of all living organisms and ammonia is the biologically usable form of nitrogen.  The mechanism by which levels of ammonia are regulated in the cell remains largely unknown.  However, the ammonia channel protein Amt1, and the signaling protein GlnK1 are believed to play a role in the process of ammonia uptake.  By determining the structure of GlnK1 protein bound to different effectors, Yildiz et al. (2007) studied the interactions and mechanism of the association of Amt and GlnK1 and how they might control ammonia uptake. These studies contribute to understanding the role of GlnK1 in nitrogen uptake and metabolism.