A New Alkalitolerant Yarrowia lipolytica Yeast Strain Is a Promising Model for Dissecting Properties and Regulation of Na⁺-Dependent Phosphate Transport Systems

---

R. A. Zvyagilskaya^1* and B. L. Persson²

¹Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, Moscow 119071, Russia; fax: (7-095) 954-2732; E-mail: renata_z@inbi.ras.ru

²Department of Biochemistry and Biophysics, Stockholm University, S-106 91 Stockholm, and Department of Chemistry and Biomedical Sciences, Kalmar University, S-391 82 Kalmar, Sweden

^* To whom correspondence should be addressed.

Received July 9, 2004

---

A newly isolated osmo-, salt-, and alkalitolerant Yarrowia lipolytica yeast strain is distinguished from other yeast species by its capacity to grow vigorously at alkaline pH values (9.7), which makes it a promising model organism for studying Na⁺-dependent phosphate transport systems in yeasts. Phosphate uptake by Y. lipolytica cells grown at pH 9.7 was mediated by several kinetically discrete Na⁺-dependent systems specifically activated by Na⁺. One of these, a low-affinity transporter, operated at high concentrations of extracellular phosphate. The other two, high-affinity systems, maximally active in phosphate-starved cells, were repressed or derepressed depending on the prevailing extracellular phosphate concentration and pH value. The contribution of Na⁺/P_i-cotransport systems to the total cellular phosphate uptake progressively increased with increasing pH, reaching its maximum at pH >= 9.

---

KEY WORDS: Yarrowia lipolytica, yeast, cytoplasmic membrane, phosphate transport, Na⁺/P_i-cotransport system, regulation

---