This group contains proteins of unknown function related to characterized cell surface adhesion proteins with a left-handed beta-roll, like the UspA1 Head And Neck Domain and YadA of Yersinia. UspA1 and UspA2 are part of a class of pathogenicity factors that act as cell surface adhesion molecules, in which N-terminal head and neck domains extend from the bacterial outer membrane. The UspA1 head domain of Moraxella catarrhalis, is formed from trimeric beta-helices of 14-16 amino acid repeats. The UspA1 head domain connects to a neck region of large extended, charged loops that maybe be ligand binding, which is in turn connected to an extended coiled coil domain that tethers the head and neck region to the cell surface via a transmembrane region. The collagen-binding domain virulence factor YadA an adhesion proteins of several Yersinia species, and related cell surface proteins. The collagen-binding portion is found in the hydrophobic N-terminal region. YadA forms a matrix on the bacterial outer membrane, which mediates binding to collagen and epithelial cells. YadA inhibits the complement-activating pathway with the coating of the cell surface with factor H, which impedes C3b molecules. These domains form a left handed beta roll made up of a series of short repeated elements.
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