The stm1⁺ (SPAC17C9.10) gene of Schizosaccharomyces pombe is closely related to genes encoding vacuolar PQ-loop proteins, Ypq1, Ypq2, and Ypq3, of Saccharomyces cerevisiae. When stm1⁺ fused with GFP was expressed in fission or budding yeast, Stm1-GFP localized at the vacuolar membrane. Isolated vacuolar membrane vesicles from S. cerevisiae cells overexpressing stm1⁺ exhibited stm1⁺-dependent arginine and lysine uptake activity. Exchange activity of arginine and histidine/arginine, as observed for Ypq2 of S. cerevisiae, was also detected in the vesicles expressing stm1⁺. The expression levels of stm1⁺ in S. pombe cells significantly affected the vacuolar contents of lysine, histidine, and arginine. These results suggest that Stm1 is a vacuolar PQ-loop protein involved in the transport of basic amino acids across the vacuolar membrane.

粟酒裂殖酵母的stm1 ⁺（SPAC17C9.10）基因与酿酒酵母液泡PQ环蛋白Ypq1，Ypq2和Ypq3的编码基因密切相关。当在裂变或发芽酵母中表达与GFP融合的stm1 ^+时，Stm1-GFP位于液泡膜上。来自过表达stm1 ^+的酿酒酵母细胞的分离的液泡膜囊泡表现出stm1 ⁺依赖性的精氨酸和赖氨酸摄取活性。酿酒酵母Ypq2观察到的精氨酸和组氨酸/精氨酸的交换活性，还检测到表达stm1 ⁺的囊泡。stm1 ⁺在粟酒裂殖酵母细胞中的表达水平显着影响赖氨酸，组氨酸和精氨酸的液泡含量。这些结果表明Stm1是液泡PQ环蛋白，参与碱性氨基酸跨液泡膜的运输。