Peptide transport in Candida albicans.

Area of Science:

• Mycology
• Biochemistry
• Cell Biology

Background:

• Candida albicans is an opportunistic fungal pathogen.
• Understanding nutrient uptake mechanisms is crucial for developing targeted antifungal strategies.

Purpose of the Study:

• To investigate the uptake mechanism of trimethionine in Candida albicans.
• To characterize the kinetic and regulatory properties of this transport system.

Main Methods:

• Utilizing radiolabeled trimethionine (L-methionyl-L-methionyl-L-[METHYL-14C]methionine) for uptake studies.
• Assessing the effects of pH, temperature, metabolic inhibitors, and competing peptides on uptake.
• Analyzing the intracellular fate of trimethionine.

Main Results:

• Trimethionine uptake is mediated by a saturable system with specific pH (3.5) and temperature (37°C) optima and an apparent Km of 3.3 x 10^-5 M.
• Uptake is energy-dependent, as indicated by inhibition with sodium azide and dinitrophenol.
• Structural analogs like (Leu)3 and Gly-Met-Gly competed for uptake, while methionine and dimethionine did not, suggesting specificity.
• Trimethionine is rapidly hydrolyzed by a peptidase post-internalization.

Conclusions:

• Candida albicans possesses a distinct, high-affinity transport system for trimethionine.
• This uptake mechanism is active and specific, differentiating trimethionine from smaller methionine-containing peptides.
• The rapid intracellular hydrolysis suggests a role for trimethionine as a source of methionine or its derivatives within the cell.