Publications

• The nucleotide sequences of the rbsD, rbsA, and rbsC genes of Escherichia coli K12.

  Bell A.W., Buckel S.D., Groarke J.M., Hope J.N., Kingsley D.H., Hermodson M.A.

  The nucleotide sequences of rbsD, rbsA, and rbsC have been determined. These genes encode components of the high affinity ribose transport system in Escherichia coli, and together with the sequences of rbsB (Groarke, J.M., Mahoney, W.C., Hope, J.N., Furlong, C.E., Robb, F.T., Zalkin, H., and Hermo ... >> More

  The nucleotide sequences of rbsD, rbsA, and rbsC have been determined. These genes encode components of the high affinity ribose transport system in Escherichia coli, and together with the sequences of rbsB (Groarke, J.M., Mahoney, W.C., Hope, J.N., Furlong, C.E., Robb, F.T., Zalkin, H., and Hermodson, M.A. (1983) J. Biol. Chem. 258, 12952-12956) and rbsK (Hope, J.N., Bell, A.W., Hermodson, M.A., and Groarke, J.M. (1986) J. Biol. Chem. 261, 7663-7668), they complete the nucleotide sequence of the first five genes of the rbs operon. Nuclease S1 mapping places the transcriptional start site for the operon 29 base pairs upstream from the most likely translational start site for rbsD. The open reading frames of rbsD, rbsA, and rbsC encode proteins of 139, 501, and 321 amino acid residues, respectively. The character of the proteins varies widely, from very hydrophilic for the rbsA product to exceedingly hydrophobic for the rbsC product. The intercistronic spaces between the three genes are very short, with the stop codons of the upstream genes overlapping the ribosome-binding sites of the downstream genes. This may imply translational control of expression of these genes, the products of which presumably form a membrane-bound transport complex. << Less

  J. Biol. Chem. 261:7652-7658(1986) [PubMed] [EuropePMC]

• In vitro reassembly of the ribose ATP-binding cassette transporter reveals a distinct set of transport complexes.

  Clifton M.C., Simon M.J., Erramilli S.K., Zhang H., Zaitseva J., Hermodson M.A., Stauffacher C.V.

  Bacterial ATP-binding cassette (ABC) importers are primary active transporters that are critical for nutrient uptake. Based on structural and functional studies, ABC importers can be divided into two distinct classes, type I and type II. Type I importers follow a strict alternating access mechanis ... >> More

  Bacterial ATP-binding cassette (ABC) importers are primary active transporters that are critical for nutrient uptake. Based on structural and functional studies, ABC importers can be divided into two distinct classes, type I and type II. Type I importers follow a strict alternating access mechanism that is driven by the presence of the substrate. Type II importers accept substrates in a nucleotide-free state, with hydrolysis driving an inward facing conformation. The ribose transporter in Escherichia coli is a tripartite complex consisting of a cytoplasmic ATP-binding cassette protein, RbsA, with fused nucleotide binding domains; a transmembrane domain homodimer, RbsC2; and a periplasmic substrate binding protein, RbsB. To investigate the transport mechanism of the complex RbsABC2, we probed intersubunit interactions by varying the presence of the substrate ribose and the hydrolysis cofactors, ATP/ADP and Mg(2+). We were able to purify a full complex, RbsABC2, in the presence of stable, transition state mimics (ATP, Mg(2+), and VO4); a RbsAC complex in the presence of ADP and Mg(2+); and a heretofore unobserved RbsBC complex in the absence of cofactors. The presence of excess ribose also destabilized complex formation between RbsB and RbsC. These observations suggest that RbsABC2 shares functional traits with both type I and type II importers, as well as possessing unique features, and employs a distinct mechanism relative to other ABC transporters. << Less

  J. Biol. Chem. 290:5555-5565(2015) [PubMed] [EuropePMC]