Tasting the Terroir with Tsr (Biophysical Journal)

Often, a discriminating palate is essential for survival. In bacteria like Escherichia coli, chemical sensors analogous to taste buds cluster at the poles of its rod shape. Four such taste buds--Tsr, Tar, Tap, and Trg, collectively known as methyl-accepting chemotaxis proteins--are expressed in E. coli, each detecting distinct classes of chemical compounds (Tap and Trg are expressed at low levels). Tsr itself detects amino acids such as serine, alanine, glycine, and cysteine. Like the rest of its cohort, its functional form is as a transmembrane ?-helical trimer of dimers bound up with CheA and CheW to form an ultrasensitive switch in the inner membrane of the Gram-negative organism expressing it (1).