Protein Domain : RTX calcium-binding nonapeptide repeat IPR001343

Type	Repeat
Description	Gram-negative bacteria produce a number of proteins that are secreted into the growth medium by a mechanism by the type I secretion system that does not require a cleaved N-terminal signal sequence. These proteins, while having different functions, share two properties: they bind calcium and they contain a multiple tandem repeat of a nonapeptide [ ]. The nonapeptide is found in a group of bacterial exported proteins that includes haemolysin, cyclolysin, leukotoxin and metallopeptidases belonging to MEROPS peptidase family M10 (clan MA(M)), subfamily 10B (serralysin).It has been suggested that the internally repeated domain of haemolysin may be involved in Ca-mediated binding to erythrocytes. It has been shown that such a domain is involved in the binding of calcium ions in a parallel beta roll structure [ ].The Bordetella pertussisadenylate cyclase toxin tertiary structure has been solved. The C-terminal RTX repeats are Asp-rich, which bind calcium ions as the protein moves from the low calcium intercellular environment to a higher extracellular concentration of calcium ions. The C-terminal assembly containing the RTX repeats has been shown to form beta rolls, which prevent backsliding of the protein in the type I sectretion system conduits and accelerating secretion of the large toxin [ ].
Short Name	Hemolysn_Ca-bd