BtuB is a beta-barrel membrane protein that facilitates transport of cobalamin (vitamin B12) from the extracellular medium across the outer membrane of Escherichia coli. It is thought that binding of B12 to BtuB alters the conformation of its periplasm-exposed N-terminal residues (the TonB box), which enables subsequent binding of a TonB protein and leads to eventual uptake of B12 into the cyto...

In BtuB, the Escherichia coli TonB-dependent transporter for vitamin B12, substrate binding to the extracellular surface unfolds a conserved energy coupling motif termed the Ton box into the periplasm. This transmembrane signaling event facilitates an interaction between BtuB and the inner-membrane protein TonB. In this study, continuous-wave and pulse electron paramagnetic resonance in a nativ...

Short oligonucleotides binding complementary mRNA essential for bacterial growth could be used as antibacterials provided that they are delivered to cells. One promising oligonucleotide is peptide nucleic acid (PNA), a synthetic DNA analog with neutral peptide-like backbone. Unfortunately, bacteria do not import short oligonucleotides, including PNA, from the environment and efficient non-invas...

The research in our laboratory focuses on the role of metal ions and their complexes in structure formation and folding of nucleic acids. Large catalytic RNAs, like group II introns and some riboswitches, as well as shorter RNAs and DNAs containing modified nucleotides for the assembly of nanodevices are examined. Abundant metal ions like Mg2+ or natural metabolites like coenzyme B12 are in the...

Ravnum, S. 2000. Translational regulation of genes in Salmonella typhimurium by vitamin B12 Acta Universitatis Upsaliensis. Comprehensive Summaries of Uppsala Dissertations from the faculty of Science and Technology. 591. 52pp. Uppsala. ISBN 91-554-4874-7. In this thesis I have studied the mechanism by which vitamin B12 regulates the expression of the cob operon and the btuB gene in Salmonella ...

The Escherichia coli btuB gene encodes the outer membrane transporter for vitamin B12, the E colicins, colicin A, and bacteriophage BF23. Several series of mutant forms of BtuB resulting from the insertion of dipeptide sequences and from overlapping in-frame deletions and duplications were constructed. Strains expressing the variant genes in single and multiple copy numbers were analyzed for Bt...

The BtuB transporter mediates high-affinity binding and TonB-dependent active transport of vitamin B12 [cyanocobalamin (CNCbl)] across the outer membrane of Escherichia coli. A characteristic feature of TonB-dependent transporters is the Ton box, a conserved sequence near the N terminus and exposed to the periplasm. Crosslinking to TonB and site-directed spin labeling indicated that the Ton box...