The chemoreceptor zinc-binding domain (CZB) is found in bacterial signal transduction proteins - most frequently receptors involved in chemotaxis and motility, but also in c-di-GMP signalling and nitrate/nitrite-sensing. Originally discovered in the ...
The chemoreceptor zinc-binding domain (CZB) is found in bacterial signal transduction proteins - most frequently receptors involved in chemotaxis and motility, but also in c-di-GMP signalling and nitrate/nitrite-sensing. Originally discovered in the cytoplasmic chemoreceptor TlpD from Helicobacter pylori, it is often found C-terminal to the MCPsignal domain in cytoplasmic chemoreceptor proteins. The CZB domain contains a core sequence motif, Hxx[WFYL]x21-28Cx[LFMVI]Gx[WFLVI]x18-27HxxxH. The highly-conserved H-C-H-H residues of this motif are believed to coordinate zinc; mutating the latter two histidines of the motif to alanines abolishes Zn binding. This domain binds zinc with high affinity, with a Kd in the femtomolar range. This domain has been shown in E. coli to be a zinc sensor that regulates the catalytic activity of Pfam:PF00990 [2]. This domain also binds the chemoattractant HOCl at a site very close to that of zinc. It has been shown that zinc participates in HOCl sensing by forming a redox 'Cys-Zn switch' that reacts towards HOCl (Matilla et. al.,FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043).
This domain is found linked to a wide range of non-homologous domains in a variety of bacteria. It has been shown to be homologous to the adenylyl cyclase catalytic domain [1] and has diguanylate cyclase activity [4]. This observation correlates with ...
This domain is found linked to a wide range of non-homologous domains in a variety of bacteria. It has been shown to be homologous to the adenylyl cyclase catalytic domain [1] and has diguanylate cyclase activity [4]. This observation correlates with the functional information available on two GGDEF-containing proteins, namely diguanylate cyclase and phosphodiesterase A of Acetobacter xylinum, both of which regulate the turnover of cyclic diguanosine monophosphate. In the WspR protein of Pseudomonas aeruginosa, the GGDEF domain acts as a diguanylate cyclase, PDB:3bre, when the whole molecule appears to form a tetramer consisting of two symmetrically-related dimers representing a biological unit. The active site is the GGD/EF motif, buried in the structure, and the cyclic dimeric guanosine monophosphate (c-di-GMP) bind to the inhibitory-motif RxxD on the surface. The enzyme thus catalyses the cyclisation of two guanosine triphosphate (GTP) molecules to one c-di-GMP molecule [6,7,8].
