Individual chaperones required for Yop secretion by Yersinia

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Pathogenic Yersinia species utilize a Type III secretion system to inject effector proteins, known as Yops, into host cells.
• Yop secretion occurs through a Sec-independent pathway, and Yops lack classical signal peptides, posing a unique secretion challenge.
• Previously, SycE was identified as a specific cytosolic chaperone for YopE secretion.

Purpose of the Study:

• To identify and characterize novel cytosolic chaperones involved in the Sec-independent secretion of Yops.
• To elucidate the roles of these chaperones in the secretion pathway of specific Yops, such as YopH, YopB, and YopD.

Main Methods:

• Genetic analysis involving mutagenesis of genes encoding putative chaperones.
• Biochemical assays, including co-immunoprecipitation and binding studies with hybrid proteins.
• Analysis of Yop protein localization and secretion levels in wild-type and mutant strains.

Main Results:

• A novel 16-kDa acidic protein, designated SycH, was identified as essential for YopH secretion. Its absence led to cytoplasmic accumulation of YopH.
• A mutation in lcrH, encoding a 19-kDa acidic protein (SycD), abolished the secretion of YopB and YopD.
• SycD was shown to associate with cytoplasmic YopD, suggesting a specific chaperone role.

Conclusions:

• SycH and SycD are identified as specific cytosolic chaperones required for the secretion of YopH, YopB, and YopD, respectively.
• SycE, SycH, and SycD represent a newly characterized family of cytosolic chaperones essential for Yop secretion in pathogenic Yersinia.
• These findings advance the understanding of the complex Sec-independent Yop secretion machinery.