4.6 Article

Topological analyses of the L-lysine exporter LysO reveal a critical role for a conserved pair of intramembrane solvent-exposed acidic residues

Journal

JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 297, Issue 4, Pages -

Publisher

ELSEVIER
DOI: 10.1016/j.jbc.2021.101168

Keywords

-

Funding

  1. Department of Biotechnology (DBT), Government of India
  2. Indian Institute of Science-GATE PhD fellowship
  3. DBT/Wellcome Trust-India Alliance Intermediate Fellowship [IA/I/15/2/502063]
  4. DBT-IISc phase II program
  5. DST-FIST program

Ask authors/readers for more resources

The study elucidated the membrane topology and export mechanism of LysO protein, suggesting that Thl may be exported in antiport with H+ while Lys may be a low-affinity export substrate. This finding provides insight into how LysO mediates Lys/Thl export and affords protection from Thl toxicity in Escherichia coli.
LysO, a prototypical member of the LysO family, mediates export of L-lysine (Lys) and resistance to the toxic Lys anti metabolite, L-thialysine (Thl) in Escherichia coli. Here, we have addressed unknown aspects of LysO function pertaining to its membrane topology and the mechanism by which it mediates Lys/Thl export. Using substituted cysteine (Cys) accessibility, here we delineated the membrane topology of LysO. Our studies support a model in which both the N-and C-termini of LysO are present at the periplasmic face of the membrane with a transmembrane (TM) domain comprising eight TM segments (TMSs) between them. In addition, a feature of intramembrane solvent exposure in LysO is inferred with the identification of membrane-located solvent-exposed Cys residues. Isosteric substitutions of a pair of conserved acidic residues, one E233, located in the solvent-exposed TMS7 and the other D261, in a solvent-exposed intramembrane segment located between TMS7 and TMS8, abolished LysO function in vivo. Thl, but not Lys, elicited proton release in inside-out membrane vesicles, a process requiring the presence of both E233 and D261. We postulate that Thl may be exported in antiport with H+ and that Lys may be a low-affinity export substrate. Our findings are compatible with a physiological scenario wherein in vivo LysO exports the naturally occurring antimetabolite Thl with higher affinity over the essential cellular metabolite Lys, thus affording protection from Thl toxicity and limiting wasteful export of Lys.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.6
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available