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Overview
WspR from Pseudomonas aeruginosa is a response regulator with an catalytic, diguanylate cyclase, output domain. It is composed of a canonical CheY-like response regulator receiver domain (Rec) and a C-terminal catalytic GGDEF domain domain that confers the catalytic activity with all canonical active site residues present.
Although not modified (i.e. phosphorylated) at the active Asp (Asp70), the Rec domains mediate formation of dimeric WspR. Two dimers, in turn, are associated by head-to-head contact to a tetramer of approximate 222 (D2) symmetry.
Allosteric product binding site
WspR (3bre)
There are two allosteric sites (primary inhibition site, Ip, and secondary inhibition site, Is) that become cross-linked by (c-di-GMP)2 dimers in the tetrameric molecule. For a close-up click here (Ip-site, Is-site, (c-di-GMP dimer)2). Note that there are four (c-di-GMP)2 dimers per WspR tetramer.