title: BspA (CyuC) in Lactobacillus fermentum BR11 is a highly expressed high-affinity L-cystine-binding protein.
abstract: The BspA protein of Lactobacillus fermentum BR11 (BR11) is a cell envelope constituent that is similar to known solute-binding proteins and putative adhesins. BspA is required for L-cystine uptake and oxidative defense and is likely to be an L-cystine-binding protein. The aim of this study was to directly measure L-cystine-BspA binding and BspA expression. De-energized BR11 cells bound radiolabelled L-cystine with a Kd of 0.2 microM. A bspA mutant could not bind L-cystine. L-cystine-BR11 binding was unaffected by large excesses of L-glutamine, L-methionine, or collagen, indicating L-cystine specificity. BR11 and the bspA mutant were identical in their abilities to bind L-cysteine, indicating that L-cysteine is not a BspA ligand. BspA expression levels were deduced from radiolabelled L-cystine binding and it was found that there are 1-2 x 10(5) BspA molecules per cell, and that expression is slightly higher under oxidizing conditions. It is proposed that BspA be renamed CyuC.
authors.affiliation: Infectious Disease Program, Science Research Centre, Queensland University of Technology, Brisbane, Australia.
authors.forename: Jacky
authors.initials: J
authors.lastname: Hung
authors.forename: Mark S
authors.initials: MS
authors.lastname: Turner
authors.forename: Terry
authors.initials: T
authors.lastname: Walsh
authors.forename: Philip M
authors.initials: PM
authors.lastname: Giffard
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism*; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D003553:Cystine / Q000378:metabolism*; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C105995:BspA protein, bacteria; D002352:Carrier Proteins; D008565:Membrane Proteins; D003553:Cystine