PMID:24699373

Citation	Usami, Y, Uemura, S, Mochizuki, T, Morita, A, Shishido, F, Inokuchi, JI and Abe, F' (2014) Functional mapping and implications of substrate specificity of the yeast high-affinity leucine permease Bap2. Biochim. Biophys. Acta '
Abstract	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 I109/G110/T111 and E305 were located within the putative α-helix break in TMD1 and TMD6, respectively, according to the structurally homologous Escherichia coli arginine/agmatine antiporter AdiC. Upon leucine binding, these α-helix breaks were assumed to mediate a conformational transition in Bap2 from an outward-open to a substrate-binding occluded state. Residues Y336 (TMD7) and Y181 (TMD3) were located near I109 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.
Links	PubMed Online version:10.1016/j.bbamem.2014.03.018
Keywords
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
YEAST:BAP2		GO:1990122: leucine import into cell	ECO:0000315:		P		Figure 1A shows the OD concentrations of leucine from a cell for both wild types strains and for mutant strains. The wild type, with a BAP2 gene, has the highest OD of leucine and the mutants have decreased ODs.	complete CACAO 10100
YEAST:BAP2	involved_in	GO:0098713: leucine import across plasma membrane	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

See Help:References for how to manage references in GONUTS.