Relative Rates of Amino Acid Import via the ABC Transporter GlnPQ Determine the Growth Performance of Lactococcus lactis

摘要: ABSTRACT The GlnPQ transporter from Lactococcus lactis has the remarkable feature of having two substrate-binding domains (SBDs) fused to N terminus transmembrane domain (TMD), and thus four SBDs are present in homodimeric complex. Although X-ray structures ligand binding data available for both SBDs, little is known how different amino acids compete with each other transport via GlnPQ. Here we show a broader substrate specificity than previously thought, ability take up asparagine, glutamine, glutamic acid, albeit routes affinities. Asparagine glutamine at level SBD1 SBD2 (with differences dissociation constant), but same time interaction translocator affinity constant rate transport). outcompeted by physiological concentrations ensures high rates import essential acid glutamine. Taken together, this study demonstrates that even presence competing asparagine concentrations, capacity which matches needs cell glutamate. IMPORTANCE an ATP-binding cassette (ABC) asparagine. system various Gram-positive bacteria, including L. several pathogens. multiple these delivery transporter. Overall, our results evolved diverse substrates paths optimally acquire abundant