The role of EscD in supporting EscC polymerization in the type III secretion system of enteropathogenic Escherichia coli

• Published in: Biochimica et biophysica acta. Biomembranes 2018-02, Vol.1860 (2), p.384-395
• Main Authors: Tseytin, Irit, Dagan, Avner, Oren, Sonia, Sal-Man, Neta
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Binding Sites - genetics; Cell Membrane - chemistry; Cell Membrane - metabolism; Enteropathogenic E. coli; Enteropathogenic Escherichia coli - genetics; Enteropathogenic Escherichia coli - metabolism; Enteropathogenic Escherichia coli - pathogenicity; EscD; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Immunoblotting; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Polymerization; Protein Binding; Protein Multimerization; Protein oligomerization; Transmembrane domains; Type 3 secretion system; Type III Secretion Systems - chemistry; Type III Secretion Systems - genetics; Type III Secretion Systems - metabolism; Virulence - genetics
• ISSN: 0005-2736; 1879-2642
• DOI: 10.1016/j.bbamem.2017.10.001

The type III secretion system (T3SS) is a multi-protein complex that plays a central role in the virulence of many Gram-negative bacterial pathogens. In enteropathogenic Escherichia coli, a prevalent cause of diarrheal diseases, the needle complex base of the T3SS is formed by multi-rings: two concentric inner-membrane rings made by the two oligomerizing proteins (EscD and EscJ), and an outer ring made of a single oligomerizing protein (EscC). Although the oligomerization activity of these proteins is critical for their function and can, therefore, affect the virulence of the pathogen, the mechanisms underlying the oligomerization of these proteins have yet to be identified. In this study, we report that the proteins forming the inner-membrane T3SS rings, EscJ and EscD proteins, are crucial for the oligomerization of EscC. Moreover, we elucidate the oligomerization process of EscD and determine the contribution of individual regions of the protein to its self-oligomerization activity. We show that the oligomerization motif of EscD is located at its N-terminal portion and that its transmembrane domain can self-oligomerize, thus contributing to the self-oligomerization of the full-length EscD. [Display omitted] •The oligomerization motif of EscD is located at its N-terminal portion.•EscD transmembrane domain can self-oligomerize.•The proteins forming the inner-membrane T3SS rings, EscJ and EscD, are crucial for the oligomerization of EscC.