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Two independent type III secretion mechanisms for YopE in Yersinia enterocolitica
L W Cheng1, D M Anderson, O Schneewind
1Department of Microbiology and Immunology and Molecular Biology Institute, UCLA School of Medicine, Los Angeles, California 90095, USA.
Abstract:
Pathogenic Yersinia species escape the infected host's defense mechanisms by targeting cytotoxic Yop proteins into the cytoplasm of macrophages via a type III secretion pathway. Two separate secretion signals contained in YopE were identified, each of which were sufficient but not necessary for the secretion of reporter molecules. One signal is located within the coding sequence of the first 15 amino acids and is sufficient for the secretion of fusion proteins but not required for YopE secretion. The second signal is located downstream at residues 15-100 of YopE and is only recognized by the type III machinery when it is bound to SycE. We propose the existence of two independent mechanisms that allow for the secretion of Yop proteins.
Insights
Pathogenic Yersinia bacteria use a type III secretion system to inject Yop proteins into host macrophages. Researchers found two distinct secretion signals in YopE, suggesting dual mechanisms for Yop protein delivery.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- Pathogenic Yersinia species employ a type III secretion system (T3SS) to deliver effector proteins, known as Yops, into host immune cells.
- These Yops are crucial for bacterial virulence, enabling pathogens to evade host defenses, particularly by targeting macrophages.
Purpose of the Study:
- To investigate the secretion signals within the YopE protein, a key effector of Yersinia.
- To elucidate the mechanisms by which YopE is translocated into host cells via the T3SS.
Main Methods:
- Utilized reporter assays to identify functional secretion signals within the YopE protein sequence.
- Investigated the role of the chaperone SycE in the recognition and secretion of YopE by the T3SS.
Main Results:
- Identified two distinct secretion signals within YopE.
- The first signal, located in the N-terminal 15 amino acids, is sufficient for reporter protein secretion but not essential for YopE secretion.
- The second signal, found in residues 15-100, requires binding to the chaperone SycE for recognition by the T3SS.
Conclusions:
- YopE secretion is mediated by at least two independent mechanisms.
- These findings provide insights into the complex regulation of T3SS effector translocation.
- Understanding these mechanisms can inform strategies to combat Yersinia infections.