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Escherichia coli hemolysin mutants with altered target cell specificity
1Department of Medical Microbiology and Immunology, University of Wisconsin--Madison 53706, USA.
Infection and Immunity
|August 1, 1996
Summary
HlyC-dependent acylation of Escherichia coli hemolysin (HlyA) is crucial for its function. Mutations in HlyA, particularly at positions K563 and K689, significantly impact its cytotoxic activity, revealing key structural roles for specific residues.
Area of Science:
- Microbiology
- Protein biochemistry
- Toxicology
Background:
- Escherichia coli hemolysin (HlyA) is a pore-forming toxin requiring HlyC-dependent acylation for full activity.
- Understanding the functional significance of HlyA acylation is key to elucidating RTX toxin mechanisms.
Purpose of the Study:
- To investigate the role of specific lysine residues (HlyAK563 and HlyAK689) in HlyC-dependent acylation of HlyA.
- To determine the impact of these acylation modifications on HlyA's cytotoxic activity against various cell types.
Main Methods:
- Site-directed and random mutagenesis of HlyA at K563 and K689 residues.
- Screening for loss of immunoreactivity to a specific monoclonal antibody (D12).
- Assessing the cytolytic activity of HlyA mutants against sheep erythrocytes, BL-3, and Raji cells.
Main Results:
- Substitutions at HlyAK563 and HlyAK689 resulted in varying degrees of reduced cytotoxicity.
- A minimal sequence (12% of HlyA) is sufficient for HlyC-facilitated acylation at HlyAK689.
- Mutations at HlyAG688 significantly impaired cytotoxic activity, suggesting a critical structural role.
Conclusions:
- HlyC-dependent acylation at HlyAK563 and HlyAK689 is essential for HlyA's full cytotoxic potential.
- The glycine at HlyAG688 plays a vital structural role in HlyA activity, independent of acylation.
- The study provides insights into the conserved structural requirements for RTX toxin activation by HlyC.