Heterologous expression of Candida utilis carboxylic acid transporters in Saccharomyces cerevisiae

Abstract

Carboxylic acids are important platform chemicals used traditionally and industrially in food and pharmaceutical companies. In the yeast Saccharomyces cerevisiae, two permeases are responsible for the uptake of carboxylates at the plasma membrane. The JEN1 gene encodes a monocarboxylate proton symporter, with specificity for lactate, pyruvate acetate and propionate, that belongs to the Major Facilitator Superfamily (TC 2.A.1.12.2) [1]. The ADY2 gene is a member of the Acetate Uptake Transporter (AceTr) Family (TC 2.A.96.1.4) and encodes an acetate transporter [2]. In the yeast Candida utilis, different uptake systems for carboxylic acids were functionally characterized [3] however until now the genes encoding these transporters remain unidentified. In this work, carboxylic acid transporter homolog genes from C. utilis were identified and expressed in Saccharomyces cerevisiae. The C. utilis ScJEN1 and ScADY2 homologs were identified through sequence alignment with BlastP and phylogenetic analysis of putative transporters. In Candida utilis, 5 genes homolog to ScJEN1 (Cjj23088, Cjj21966, Cjj22358, Cjj21989, Cjj21602) and 4 genes homolog to ScADY2 (Cja24587, Cja20823, Cja20690, Cja20822) were identified. These genes were expressed under the control of a GPD constitutive promoter, in a S. cerevisiae jen1∆ady2∆ strain, that presents no activity for plasma membrane carboxylate permeases. The functional characterization of these proteins is currently underway.