Abstract
We have identified YkbA from Bacillus subtilis as a novel member of the L-amino acid transporter (LAT) family of amino acid transporters. The protein is approximately 30% identical in amino acid sequence to the light subunits of human heteromeric amino acid transporters. Purified His-tagged YkbA from Escherichia coli membranes reconstituted in proteoliposomes exhibited sodium-independent, obligatory exchange activity for L-serine and L-threonine and also for aromatic amino acids, albeit with less activity. Thus, we propose that YkbA be renamed SteT (Ser/Thr exchanger transporter). Kinetic analysis supports a sequential mechanism of exchange for SteT. Freeze-fracture analysis of purified, functionally active SteT in proteoliposomes, together with blue native polyacrylamide gel electrophoresis and transmission electron microscopy of detergent-solubilized purified SteT, suggest that the transporter exists in a monomeric form. Freeze-fracture analysis showed spherical particles with a diameter of 7.4 nm. Transmission electron microscopy revealed elliptical particles (diameters 6 x 7 nm) with a distinct central depression. To our knowledge, this is the first functional characterization of a prokaryotic member of the LAT family and the first structural data on an APC (amino acids, polyamines, and choline for organocations) transporter. SteT represents an excellent model to study the molecular architecture of the light subunits of heteromeric amino acid transporters and other APC transporters.
Highlights
We have identified YkbA from Bacillus subtilis as a novel member of the L-amino acid transporter (LAT) family of amino acid transporters
LAT family members correspond to the light subunits of the heteromeric amino acid transporters (HATs), called glycoprotein-associated amino acid transporters [2,3,4]
Screening for an Appropriate Prokaryotic Homolog Candidate of LAT Transporters—In order to identify appropriate prokaryotic homolog candidates for studying the structure-function relationships of the light subunits of HATs, an exhaustive search was made on several available protein sequence data bases
Summary
We have identified YkbA from Bacillus subtilis as a novel member of the L-amino acid transporter (LAT) family of amino acid transporters. This is the first functional characterization of a prokaryotic member of the LAT family and the first structural data on an APC (amino acids, polyamines, and choline for organocations) transporter.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
