Unidirectional arginine transport in reconstituted plasma‐membrane vesicles from yeast overexpressing CAN1

Abstract

Amino acids are accumulated in Saccharomyces cerevisiae by strictly unidirectional influx systems. To see whether cellular compartmentation causes this unusual amino‐acid‐transport behaviour, arginine transport was studied in plasma‐membrane vesicles. The arginine permease gene CANI was overexpressed in S. cerevisiae RH218a and in a permease‐deficient mutant RS453 (canl). Reconstituted piasma‐membrane vesicles from these transformants, energized by incorporated cytochrome‐c oxidase, showed 3–4‐fold increased rates of arginine uptake compared to vesicles from wild‐type cells. The KT values were 32.5 μM in vesicles from wild‐type and 28.6 μM in vesicles from transformed cells; the corresponding in vivo values were 17.5 μM and 11.4 μM, respectively. It could be demonstrated that unidirectional arginine transport and accumulation also exist in vesicles; thus, unidirectional influx is not related to cellular compartmentation. Copyright © 1993, Wiley Blackwell. All rights reserved