High resolution structure of an alternate form of the ferric ion binding protein from XXXX .

@entity1522 @entity526 @entity327 @entity72332 @entity1391 @entity367 @entity1098 @entity68
The periplasmic @entity68 binding protein of pathogenic Gram-negative bacteria performs an essential role in @entity68 acquisition from transferrin and other @entity68 sources. Structural analysis of this protein from @entity327 identified four @entity1522 that ligand the bound @entity68 : His(9), @entity367 (57), Tyr(195), and Tyr(196). A phosphate provides an additional ligand, and the presence of a water molecule is required to complete the octahedral geometry for stable @entity68 binding. We report the 1.14-A resolution crystal structure of the @entity68 -loaded form of the @entity327 periplasmic ferric ion binding protein (FbpA) mutant @entity72332 . This protein was produced in the periplasm of @entity526 and, after purification and conversion to the apo form, was @entity68 -loaded. H9Q is able to bind ferric @entity68 in an open conformation. A surprising finding in the present high resolution structure is the presence of @entity1098 located at the previously determined anion ternary binding site, where @entity1391 is located in the wild type holo and apo structures. @entity1098 contributes four of the six coordinating ligands for @entity68 , with two Tyr residues, 195 and 196, completing the coordination. This is the first example of a metal binding protein with a bound metal. @entity1098 complex. The results suggest that FbpA may have the ability to bind and transport @entity68 bound to biological chelators, in addition to bare ferric @entity68 .
