期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
卷 1838, 期 7, 页码 1719-1729出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbamem.2014.03.018
关键词
Saccharomyces cerevisiae; Leucine permease Bap2; Homology modeling; logP
资金
- Japan Society for the Promotion of Science [22658031, 24580122]
- Program for the Strategic Research Foundation at Private Universities by the Ministry of Education, Culture, Sports, Science, and Technology
- Grants-in-Aid for Scientific Research [23370064, 22658031, 24580122, 26110717] Funding Source: KAKEN
Leucine is a major amino acid in nutrients and proteins and is also an important precursor of higher alcohols during brewing. In Saccharomyces cerevisiae, leucine uptake is mediated by multiple amino acid permeases, including the high-affinity leucine permease Bap2. Although BAP2 transcription has been extensively analyzed, the mechanisms by which a substrate is recognized and moves through the permease remain unknown. Recently, we determined 15 amino acid residues required for Tat2-mediated tryptophan import. Here we introduced homologous mutations into Bap2 amino acid residues and showed that 7 residues played a role in leucine import Residues 1109/G110/T111 and E305 were located within the putative a-helix break in TMD1 and TMD6, respectively, according to the structurally homologous Escherichia coli arginine/agmatine antiporter AdiC. Upon leucine binding, these a-helix breaks were assumed to mediate a conformational transition in Bap2 from an outward-open to a substratebinding occluded state. Residues Y336 (TMD7) and Y181 (TMD3) were located near 1109 and E305, respectively. Bap2-mediated leucine import was inhibited by some amino acids according to the following order of severity: phenylalanine, leucine > isoleucine > methionine, tyrosine > valine > tryptophan; histidine and asparagine had no effect. Moreover, this order of severity clearly coincided with the logP values (octanol-water partition coefficients) of all amino acids except tryptophan. This result suggests that the substrate partition efficiency to the buried Bap2 binding pocket is the primary determinant of substrate specificity rather than structural amino acid side chain recognition. (C) 2014 Elsevier B.V. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据