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Basis for the design of anticandidal agents from studies of peptide utilization in Canadida albicans
Abstract:
The growth of Candida albicans WD 18-4, a methionine and lysine double auxotroph, on a variety of methionine- and lysine-containing peptides was determined. This yeast does not excrete extracellular peptidases. Thus, the growth response to peptides containing the required amino acid is a measure of peptide transport. A variety of methionine-containing peptides such as Met-Met, Met-Met-Met, and Met-Met-Met-Met-Met are transported. Acylation of the N-terminus of transported peptides does not affect their transport, but derivitization of the C-terminus prevents peptide uptake. In contrast, all lysine-containing peptides tested, except Lys-Gly, were not growth substrates. The inability of a peptide to substitute for the requisite amino acid was not due to the absence of cellular peptidases or to toxicity of the nonutilized peptides. Several potentially toxic amino acids were carried into Candida as a component of transported peptides. This establishes the peptide transport system as a possible tool for the design of antibiotics for Candida albicans.
Insights
Candida albicans can transport methionine-rich peptides, but not most lysine-containing ones, indicating specific peptide uptake mechanisms. This finding suggests peptide transporters could be targets for developing new antifungal antibiotics.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- Candida albicans is an opportunistic fungal pathogen.
- Understanding nutrient uptake in C. albicans is crucial for developing targeted therapies.
- Methionine and lysine auxotrophy in C. albicans WD 18-4 necessitates specific nutrient acquisition pathways.
Purpose of the Study:
- To investigate the peptide transport capabilities of Candida albicans WD 18-4.
- To determine the specificity of peptide uptake for methionine- and lysine-containing peptides.
- To assess the potential of C. albicans peptide transport systems as targets for antifungal drug development.
Main Methods:
- Culturing the methionine and lysine double auxotroph Candida albicans WD 18-4.
- Assessing yeast growth on various synthetic peptides containing methionine or lysine.
- Analyzing the effect of N- and C-terminal modifications on peptide transport.
- Evaluating the role of extracellular and intracellular peptidases in peptide utilization.
Main Results:
- Candida albicans WD 18-4 efficiently transports multiple methionine-containing peptides (e.g., Met-Met, Met-Met-Met).
- Transport of methionine peptides is unaffected by N-terminal acylation but blocked by C-terminal derivatization.
- Most tested lysine-containing peptides, except Lys-Gly, are not utilized as growth substrates.
- The yeast lacks extracellular peptidases, and peptide transport does not result from toxicity or absence of intracellular peptidases.
Conclusions:
- Candida albicans possesses specific peptide transport systems for methionine-containing peptides.
- Lysine uptake via peptides appears highly restricted, with Lys-Gly being an exception.
- The characterized peptide transport mechanisms offer a potential avenue for designing novel antifungal agents targeting Candida albicans.