Putative catalytic NodB homology domain of PgaB, IcaB, and similar proteins which consist of a deformed (beta/alpha)8 barrel fold with 5- or 6-strands
This family belongs to the large and functionally diverse carbohydrate esterase 4 (CE4) superfamily, whose members show strong sequence similarity with some variability due to their distinct carbohydrate substrates. It includes bacterial poly-beta-1,6-N-acetyl-D-glucosamine N-deacetylase PgaB, hemin storage system HmsF protein in gram-negative species, intercellular adhesion proteins IcaB, and many uncharacterized prokaryotic polysaccharide deacetylases. It also includes a putative polysaccharide deacetylase YxkH encoded by the Bacillus subtilis yxkH gene, which is one of six polysaccharide deacetylase gene homologs present in the Bacillus subtilis genome. Sequence comparison shows all family members contain a conserved domain similar to the catalytic NodB homology domain of rhizobial NodB-like proteins, which consists of a deformed (beta/alpha)8 barrel fold with 6 or 7 strands. However, in this family, most proteins have 5 strands and some have 6 strands. Moreover, long insertions are found in many family members, whose function remains unknown.