E2~Ub conjugates regulate the kinase activity of Shigella effector OspG during pathogenesis

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Pathogenic bacteria deliver effector proteins into host cells to facilitate invasion.
• Shigella effector OspG kinase suppresses host inflammatory responses.
• OspG interacts with host E2 ubiquitin-conjugating enzymes activated with ubiquitin (E2~Ub).

Purpose of the Study:

• To investigate the structural and functional consequences of OspG binding to E2~Ub conjugates.
• To elucidate the role of E2~Ub conjugates in regulating OspG kinase activity.
• To understand how OspG utilizes E2~Ub interactions for bacterial pathogenesis.

Main Methods:

• Co-crystallography of OspG with UbcH5c~Ub.
• Biochemical assays to measure kinase activity.
• In vivo mouse oral infection models.

Main Results:

• OspG binding stabilizes an active conformation of the kinase, significantly increasing its activity.
• OspG binding induces an inactive conformation in UbcH5c~Ub.
• OspG interacts with at least ten human E2~Ub enzymes, suggesting broad regulatory potential.
• E2~Ub conjugates act as novel regulators of OspG function in vivo.

Conclusions:

• OspG is a minimal kinase whose activity is allosterically regulated by E2~Ub binding.
• The interaction between OspG and E2~Ub conjugates is a critical mechanism for modulating host responses during Shigella infection.
• E2~Ub conjugates represent a new class of regulators for bacterial effector kinases.