The substrate-binding protein TeaA of the osmoregulated ectoine transporter TeaABC fromHalomonas elongata: purification and characterization of recombinant TeaA

TeaABC is a novel, osmoregulated secondary transport system for compatible solutes found in the halophilic proteobacterium Halomonas elongata DSM 2581(T). Sequence comparisons have confirmed that TeaABC belongs to the family of TRAP transporters and as such it consists of two putative transmembrane proteins (TeaB, TeaC) and a putative periplasmic substrate-binding protein (TeaA). TeaABC is the only osmoregulated transporter for ectoines found in H. elongata. By overexpressing TeaA-(6)His tag in Escherichia coli we demonstrated that TeaA is processed as predicted and exported to the periplasm. Furthermore, it was proven that TeaA is indeed a periplasmic ectoine-binding protein. The functionality of the purified protein as an ectoine-binding protein was tested employing a modified binding assay.