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Characterization of the binding surface of the translocated intimin receptor, an essential protein for EPEC and EHEC cell adhesion
Author(s) -
Ross Nathan T.,
Miller Benjamin L.
Publication year - 2007
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.073128607
Subject(s) - intimin , isothermal titration calorimetry , biology , bacterial outer membrane , enteropathogenic escherichia coli , escherichia coli , binding site , biophysics , microbiology and biotechnology , biochemistry , enterobacteriaceae , gene
Abstract The translocated intimin receptor (TIR) of enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) is required for EPEC and EHEC infections, which cause widespread illness across the globe. TIR is translocated via a type‐III secretion system into the intestinal epithelial cell membrane, where it serves as an anchor for E. coli attachment via its binding partner intimin. While many aspects of EPEC and EHEC infection are now well understood, the importance of the intermolecular contacts made between intimin and TIR have not been thoroughly investigated. Herein we report site‐directed mutagenesis studies on the intimin‐binding domain of EPEC TIR, and how these mutations affect TIR‐intimin association, as analyzed by isothermal titration calorimetry and circular dichroism. These results show how two factors govern TIR's binding to intimin: A three‐residue TIR hot spot is identified that largely mediates the interaction, and mutants that alter the β‐hairpin structure of TIR severely diminish binding affinity. In addition, peptides incorporating key TIR residues identified by mutagenesis are incapable of binding intimin. These results indicate that hot spot residues and structural orientation/preorganization are required for EPEC, and likely EHEC, TIR‐intimin binding.