Regenberg B, Düring-Olsen L, Kielland-Brandt M C, Holmberg S
Department of Yeast Genetics, Carlsberg Laboratory, Copenhagen Valby, Denmark.
Curr Genet. 1999 Dec;36(6):317-28. doi: 10.1007/s002940050506.
All known amino-acid permeases (AAPs) in Saccharomyces cerevisiae belong to a single family of homologous proteins. Genes of 15 AAPs were overexpressed in different strains, and the ability to take up one or more of the 20 common L-alpha-amino acids was studied in order to obtain a complete picture of the substrate specificity for these permeases. Radiolabelled amino-acid uptake measurements showed that Agp1p is a general permease for most uncharged amino acids (Ala, Gly, Ser, Thr, Cys, Met, Phe, Tyr, Ile, Leu, Val, Gln and Asn). Gnp1p, which is closely related to Agp1p, has a somewhat less-broad specificity, transporting Leu, Ser, Thr, Cys, Met, Gln and Asn, while Bap2p and Bap3p, which are also closely related to Agp1p, are able to transport Ile, Leu, Val, Cys, Met, Phe, Tyr and Trp. All four permeases are transcriptionally induced by an extracellular amino acid, but differ in expression with respect to the nitrogen source. On a non-repressive nitrogen source, AGP1 is induced, while GLN1, BAP2 and BAP3 are not. Except for Dip5p, which is a transporter for Glu, Asp, Gln, Asn, Ser, Ala and Gly, the rest of the permeases exhibit narrow specificity. Tat2p can take up Phe, Trp and Tyr; Put4p can transport Ala, Gly and Pro; while Can1p, Lyp1p and the previously uncharacterized Alp1p are specific for the cationic amino acids. These findings modify the prevalent view that S. cerevisiae only contains one general amino-acid permease, Gap1p, and a number of permeases that are specific for a single or a few amino acids.
酿酒酵母中所有已知的氨基酸通透酶（AAPs）都属于一个同源蛋白家族。15种AAPs的基因在不同菌株中过表达，并研究了它们摄取20种常见L-α-氨基酸中一种或多种的能力，以便全面了解这些通透酶的底物特异性。放射性标记氨基酸摄取测量结果表明，Agp1p是大多数不带电荷氨基酸（丙氨酸、甘氨酸、丝氨酸、苏氨酸、半胱氨酸、甲硫氨酸、苯丙氨酸、酪氨酸、异亮氨酸、亮氨酸、缬氨酸、谷氨酰胺和天冬酰胺）的通用通透酶。与Agp1p密切相关的Gnp1p，其特异性略窄，转运亮氨酸、丝氨酸、苏氨酸、半胱氨酸、甲硫氨酸、谷氨酰胺和天冬酰胺，而与Agp1p也密切相关的Bap2p和Bap3p能够转运异亮氨酸、亮氨酸、缬氨酸、半胱氨酸、甲硫氨酸、苯丙氨酸、酪氨酸和色氨酸。这四种通透酶均由细胞外氨基酸转录诱导，但在氮源方面的表达有所不同。在非抑制性氮源上，AGP1被诱导，而GLN1、BAP2和BAP3则不被诱导。除了作为谷氨酸、天冬氨酸、谷氨酰胺、天冬酰胺、丝氨酸、丙氨酸和甘氨酸转运体的Dip5p外，其余通透酶表现出狭窄的特异性。Tat2p可以摄取苯丙氨酸、色氨酸和酪氨酸；Put4p可以转运丙氨酸、甘氨酸和脯氨酸；而Can1p, Lyp1p和之前未鉴定的Alp1p对阳离子氨基酸具有特异性。这些发现修正了普遍观点，即酿酒酵母只含有一种通用氨基酸通透酶Gap1p和一些对单一或少数氨基酸具有特异性的通透酶。
