ATOMIC-STRUCTURE AND SPECIFICITY OF BACTERIAL PERIPLASMIC RECEPTORS FOR ACTIVE-TRANSPORT AND CHEMOTAXIS - VARIATION OF COMMON THEMES

Crystallographic structure refinement at very high resolutions of a do zen periplasmic receptors has revealed that, though they have differen t sizes (26 to 60 kDa) and little sequence homology, they have high te rtiary structure similarity. They consist of two distinct globular dom ains bisected by a cleft or groove wherein the ligand binds and is bur ied by a hinge-bending motion between the two domains. Structural anal ysis also reveals how hydrogen-bonding interactions can be tailored to a wide spectrum of specificity, ranging from the stringent specificit y for phosphate and sulphate to the more loose specificity for peptide s.