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Extracellular loops matter – subcellular location and function of the lysine transporter Lyp1 from Saccharomyces cerevisiae
The FEBS Journal ( IF 5.5 ) Pub Date : 2020-02-25 , DOI: 10.1111/febs.15262 Joury S Van't Klooster 1 , Frans Bianchi 1 , Ruben B Doorn 1 , Mirco Lorenzon 1 , Jarnick H Lusseveld 1 , Christiaan M Punter 1 , Bert Poolman 1
The FEBS Journal ( IF 5.5 ) Pub Date : 2020-02-25 , DOI: 10.1111/febs.15262 Joury S Van't Klooster 1 , Frans Bianchi 1 , Ruben B Doorn 1 , Mirco Lorenzon 1 , Jarnick H Lusseveld 1 , Christiaan M Punter 1 , Bert Poolman 1
Affiliation
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Yeast amino acid transporters of the APC superfamily are responsible for the proton motive force‐driven uptake of amino acids into the cell, which for most secondary transporters is a reversible process. The l‐lysine proton symporter Lyp1 of Saccharomyces cerevisiae is special in that the Michaelis constant from out‐to‐in transport ( 
) is much lower than 
, which allows accumulation of l‐lysine to submolar concentration. It has been proposed that high intracellular lysine is part of the antioxidant mechanism of the cell. The molecular basis for the unique kinetic properties of Lyp1 is unknown. We compared the sequence of Lyp1 with APC para‐ and orthologues and find structural features that set Lyp1 apart, including differences in extracellular loop regions. We screened the extracellular loops by alanine mutagenesis and determined Lyp1 localization and activity and find positions that affect either the localization or activity of Lyp1. Half of the affected mutants are located in the extension of extracellular loop 3 or in a predicted α‐helix in extracellular loop 4. Our data indicate that extracellular loops not only connect the transmembrane helices but also serve functionally important roles.
中文翻译：
细胞外环很重要——酿酒酵母赖氨酸转运蛋白 Lyp1 的亚细胞位置和功能
APC 超家族的酵母氨基酸转运蛋白负责质子动力驱动的氨基酸摄取进入细胞，这对于大多数二级转运蛋白来说是一个可逆过程。酿酒酵母的L-赖氨酸质子同向转运蛋白Lyp1的特殊之处在于，从外到内运输的米氏常数( )远低于，这使得L-赖氨酸积累至亚摩尔浓度。有人提出，细胞内高赖氨酸是细胞抗氧化机制的一部分。Lyp1 独特动力学特性的分子基础尚不清楚。我们将 Lyp1 的序列与 APC 旁系同源物和直向同源物进行比较，发现了使 Lyp1 与众不同的结构特征，包括细胞外环区域的差异。我们通过丙氨酸诱变筛选细胞外环，确定 Lyp1 定位和活性，并找到影响 Lyp1 定位或活性的位置。一半受影响的突变体位于细胞外环 3 的延伸部分或细胞外环 4 中预测的 α 螺旋中。我们的数据表明，细胞外环不仅连接跨膜螺旋，而且还发挥重要的功能作用。
更新日期：2020-02-25
) is much lower than , which allows accumulation of l‐lysine to submolar concentration. It has been proposed that high intracellular lysine is part of the antioxidant mechanism of the cell. The molecular basis for the unique kinetic properties of Lyp1 is unknown. We compared the sequence of Lyp1 with APC para‐ and orthologues and find structural features that set Lyp1 apart, including differences in extracellular loop regions. We screened the extracellular loops by alanine mutagenesis and determined Lyp1 localization and activity and find positions that affect either the localization or activity of Lyp1. Half of the affected mutants are located in the extension of extracellular loop 3 or in a predicted α‐helix in extracellular loop 4. Our data indicate that extracellular loops not only connect the transmembrane helices but also serve functionally important roles.
中文翻译：
细胞外环很重要——酿酒酵母赖氨酸转运蛋白 Lyp1 的亚细胞位置和功能
APC 超家族的酵母氨基酸转运蛋白负责质子动力驱动的氨基酸摄取进入细胞，这对于大多数二级转运蛋白来说是一个可逆过程。酿酒酵母的L-赖氨酸质子同向转运蛋白Lyp1的特殊之处在于，从外到内运输的米氏常数( )远低于，这使得L-赖氨酸积累至亚摩尔浓度。有人提出，细胞内高赖氨酸是细胞抗氧化机制的一部分。Lyp1 独特动力学特性的分子基础尚不清楚。我们将 Lyp1 的序列与 APC 旁系同源物和直向同源物进行比较，发现了使 Lyp1 与众不同的结构特征，包括细胞外环区域的差异。我们通过丙氨酸诱变筛选细胞外环，确定 Lyp1 定位和活性，并找到影响 Lyp1 定位或活性的位置。一半受影响的突变体位于细胞外环 3 的延伸部分或细胞外环 4 中预测的 α 螺旋中。我们的数据表明，细胞外环不仅连接跨膜螺旋，而且还发挥重要的功能作用。
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