Functional complementation between bacterial MDR-like export systems: colicin V, alpha-hemolysin, and Erwinia...

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Colicin V (ColV) is an antibacterial protein secreted independently of signal sequences in gram-negative bacteria.
• The export machinery for ColV shares similarities with other signal sequence-independent systems, like those for alpha-hemolysin (Hly) and Erwinia protease (Prt).

Purpose of the Study:

• To investigate the functional complementation and signal specificity of ColV export by heterologous systems.
• To define the export signals within ColV recognized by the HlyBD exporter.

Main Methods:

• Utilizing intact and individual Hly export genes to complement ColV export-deficient strains.
• Employing gene fusions and point mutations in the ColV structural gene to identify export signals.
• Assessing functional complementation and interference between ColV, Hly, and Prt export systems.

Main Results:

• The HlyBD system successfully exported active ColV in the absence of native ColV export proteins (CvaA, CvaB).
• Individual Hly export genes showed lower efficiency in complementing ColV export mutations compared to the intact system.
• An export signal for HlyBD was localized to the N-terminal 57 amino acids of ColV.
• Mutations in the ColV export signal demonstrated differential effects on export via CvaAB and HlyBD, indicating distinct signal specificities.
• The Erwinia protease (Prt) export proteins also exported ColV, with observed interference from CvaA/CvaB.

Conclusions:

• The HlyBD system can mediate ColV export, highlighting functional overlap between distinct bacterial secretion pathways.
• ColV possesses specific export signals recognized by different secretion systems, with variations in specificity between Cva, Hly, and Prt.
• Cross-talk and interference occur when components of different signal sequence-independent export systems are co-expressed.