The uptake of amino acids by erg mutants of Candida albicans

Abstract

Polyene-resistant ergosterol-less mutants of Candida albicans were used to study the role of various accumulated sterol intermediates on amino acid transport. It was found that the uptake of a number of amino acids was reduced in erg mutant strains as compared with the wild-type 33 ERG⁺. The decrease in amino acid uptake was associated with an increase in apparent K_t and decreased J_max for most of the amino acids. The energetics of amino acid uptake remained unaffected in erg mutants since the plasma membrane ATPase activity which maintains an electrochemical gradient of protons, remained unchanged between the mutants and their wild-type. The accumulation of all the amino acids was against their concentration gradient and their steady state accumulation varied between 15- and 50-fold. The fold accumulation however, was considerably lower in the erg. 16 mutant strain (3- to 12-fold).