Mechanism of Action
DnaK Inhibition
Pyrrhocoricin is a non-membrane-lytic AMP that crosses the bacterial cell membrane without causing lysis. Inside the cell, it binds to the bacterial heat shock protein DnaK (Hsp70), inhibiting its ATPase activity and chaperone function. This interferes with protein folding and leads to accumulation of misfolded proteins, ultimately causing cell death.
SbmA Transporter Uptake
Uptake into gram-negative bacteria relies on the inner membrane transporter SbmA. Bacteria lacking SbmA are resistant to pyrrhocoricin, confirming transporter-dependent entry. This mechanism is distinct from most AMPs and has implications for resistance patterns.
Research Summary
Gram-Negative Spectrum
PreclinicalPyrrhocoricin is active primarily against gram-negative bacteria including E. coli, Salmonella, and Proteus mirabilis. Its activity against gram-positive organisms is limited, consistent with its transporter-dependent mechanism. MIC values of 1-4 mcg/mL have been reported for susceptible strains.
Resistance Development
PreclinicalStudies indicate that resistance to pyrrhocoricin emerges slowly, requiring loss of the SbmA transporter. This imposes a fitness cost on bacteria, potentially limiting resistance spread. Comparative resistance studies suggest a lower resistance potential than conventional antibiotics.
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Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| MIC against E. coli | 1-4 mcg/mL | Single | Broth assay |
| DnaK binding | 10-50 uM | Single | In vitro binding assay |
Research only. No human protocols established.
Interactions
Safety Profile
Pyrrhocoricin has a favorable safety profile compared to membrane-lytic AMPs, with low hemolytic activity. Its intracellular mechanism and dependence on a bacterial-specific transporter contribute to selectivity. No human safety data available.
References
- [1]Otvos L Jr et al. (2000). Interaction between heat shock proteins and antimicrobial peptides. Biochemistry, 39(46), 14150-14159.
- [2]Kragol G et al. (2001). The antibacterial peptide pyrrhocoricin inhibits the ATPase actions of DnaK and prevents chaperone-assisted protein folding. Biochemistry, 40(10), 3016-3026.