A Riboflavin Transporter in < b > < i > Bdellovibrio exovorous < /i > < /b > JSS

The ImpX transporters of the drug/metabolite transporter superfamily were first proposed to transport riboflavin (RF; vitamin B2) based on findings of acis-regulatory RNA element responding to flavin mononucleotide (an FMN riboswitch).Bdellovibrio exovorous JSS has a homolog belonging to this superfamily. It has 10 TMSs and shows 30% identity to the previously characterized ImpX transporter fromFusobacterium nucleatum. However, the ImpX homolog is not regulated by an FMN-riboswitch. In order to test the putative function of the ImpX homolog fromB. exovorous (BexImpX), we cloned and heterologously expressed its gene. We used functional complementation, growth inhibition experiments, direct uptake experiments and inhibition studies, suggesting a high degree of specificity for RF uptake. The EC50 for growth with RF was estimated to be in the range 0.5 –1 µM, estimated from the half-maximal RF concentration supporting the growth of a RF auxotrophicEscherichia coli strain, but the Khalf for RF uptake was 20 µM. Transport experiments suggested that the energy source is the proton motive force but that NaCl stimulates uptake. Thus, members of the ImpX family members are capable of RF uptake, not only in RF prototrophic species such asF.  nucleatum, but also in the B2 auxotrophic species,B. exovorous.J Mol Microbiol Biotechnol
Source: Journal of Molecular Microbiology and Biotechnology - Category: Microbiology Source Type: research