GH18 domain of CTS3 (chitinase 3), an uncharacterized protein from the human fungal pathogen Coccidioides posadasii. CTS3 has a chitinase-like glycosyl hydrolase family 18 (GH18) domain; and has homologs in bacteria as well as fungi.
Bacillus subtilis PhoD and related proteins, metallophosphatase domain. PhoD (also known as alkaline phosphatase D/APaseD in Bacillus subtilis) is a secreted phosphodiesterase encoded by phoD of the Pho regulon in Bacillus subtilis. PhoD homologs are found in prokaryotes, eukaryotes, and archaea. PhoD contains a twin arginine (RR) motif and is transported by the Tat (Twin-arginine translocation) translocation pathway machinery (TatAyCy). This family also includes the Fusarium oxysporum Fso1 protein. PhoD belongs to the metallophosphatase (MPP) superfamily. MPPs are functionally diverse, but all share a conserved domain with an active site consisting of two metal ions (usually manganese, iron, or zinc) coordinated with octahedral geometry by a cage of histidine, aspartate, and asparagine residues. The MPP superfamily includes: Mre11/SbcD-like exonucleases, Dbr1-like RNA lariat debranching enzymes, YfcE-like phosphodiesterases, purple acid phosphatases (PAPs), YbbF-like UDP-2,3-diacylglucosamine hydrolases, and acid sphingomyelinases (ASMases). The conserved domain is a double beta-sheet sandwich with a di-metal active site made up of residues located at the C-terminal side of the sheets. This domain is thought to allow for productive metal coordination.
The GH18 (glycosyl hydrolase, family 18) type II chitinases hydrolyze chitin, an abundant polymer of beta-1,4-linked N-acetylglucosamine (GlcNAc) which is a major component of the cell wall of fungi and the exoskeleton of arthropods. Chitinases have been identified in viruses, bacteria, fungi, protozoan parasites, insects, and plants. The structure of the GH18 domain is an eight-stranded beta/alpha barrel with a pronounced active-site cleft at the C-terminal end of the beta-barrel. The GH18 family includes chitotriosidase, chitobiase, hevamine, zymocin-alpha, narbonin, SI-CLP (stabilin-1 interacting chitinase-like protein), IDGF (imaginal disc growth factor), CFLE (cortical fragment-lytic enzyme) spore hydrolase, the type III and type V plant chitinases, the endo-beta-N-acetylglucosaminidases, and the chitolectins. The GH85 (glycosyl hydrolase, family 85) ENGases (endo-beta-N-acetylglucosaminidases) are closely related to the GH18 chitinases and are included in this alignment model.
Structure of chitinase, ChiC, from Aspergillus fumigatus. [Aspergillus fumigatus Af293],2Y8V_B Structure of chitinase, ChiC, from Aspergillus fumigatus. [Aspergillus fumigatus Af293],2Y8V_C Structure of chitinase, ChiC, from Aspergillus fumigatus. [Aspergillus fumigatus Af293],2Y8V_D Structure of chitinase, ChiC, from Aspergillus fumigatus. [Aspergillus fumigatus Af293]