Multifunctional regulatory mutation in Bacillus subtilis flavinogenesis system

Flavin Binding to the High Affinity Riboflavin Transporter RibU

“…The affinity of RibU for its substrate is comparable with the riboflavin binding affinity (K d 5-20 nM) measured in membrane vesicles of B. subtilis (27). Very likely the binding of riboflavin to B. subtilis membranes is mediated by YpaA, a homologue of RibU (5). The high binding affinity of RibU and riboflavin poses a challenge for the release of riboflavin in the cytoplasm and necessitates the internal concentration of free riboflavin to be kept low.…”

“…In vivo transport studies suggested that the protein facilitates diffusion and does not use metabolic energy for transport of riboflavin. In the bacteria Lactococcus lactis and Bacillus subtilis, two homologous riboflavin transporters, YpaA and RibU, respectively, were found (4,5). RibU is a 22.8-kDa membrane protein with five predicted membrane-spanning segments.…”