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Structure and biochemical analysis of a secretin pilot protein
Author(s) -
Lario Paula I,
Pfuetzner Richard A,
Frey Elizabeth A,
Creagh Louise,
Haynes Charles,
Maurelli Anthony T,
Strynadka Natalie C J
Publication year - 2005
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7600610
Subject(s) - biology , secretin , computational biology , biochemistry , pancreas
The ability to translocate virulence proteins into host cells through a type III secretion apparatus (TTSS) is a hallmark of several Gram‐negative pathogens including Shigella, Salmonella, Yersinia, Pseudomonas , and enteropathogenic Escherichia coli . In common with other types of bacterial secretion apparatus, the assembly of the TTSS complex requires the preceding formation of its integral outer membrane secretin ring component. We have determined at 1.5 Å the structure of MxiM 28–142 , the Shigella pilot protein that is essential for the assembly and membrane association of the Shigella secretin, MxiD. This represents the first atomic structure of a secretin pilot protein from the several bacterial secretion systems containing an orthologous secretin component. A deep hydrophobic cavity is observed in the novel ‘cracked barrel’ structure of MxiM, providing a specific binding domain for the acyl chains of bacterial lipids, a proposal that is supported by our various lipid/MxiM complex structures. Isothermal titration analysis shows that the C‐terminal domain of the secretin, MxiD 525–570 , hinders lipid binding to MxiM.