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Umeå, Sweden

Bylund G.O.,Umea University | Bylund G.O.,Helicure AB | Nord S.,Umea University | Lovgren J.M.,Umea University | And 2 more authors.
Journal of Bacteriology | Year: 2011

The RimM protein in Escherichia coli is important for the in vivo maturation of 30S ribosomal subunits and a ΔrimM mutant grows poorly due to assembly and translational defects. These deficiencies are suppressed partially by mutations that increase the synthesis of another assembly protein, RbfA, encoded by the metYnusA-infB operon. Among these suppressors are mutations in nusA that impair the NusA-mediated negativefeedback regulation at internal intrinsic transcriptional terminators of the metY-nusA-infB operon. We describe here the isolation of two new mutations, one in rpoB and one in rpoC (encoding the β and β' subunits of the RNA polymerase, respectively), that increase the synthesis of RbfA by preventing NusA from stimulating termination at the internal intrinsic transcriptional terminators of the metY-nusA-infB operon. The rpoB2063 mutation changed the isoleucine in position 905 of the β' flap-tip helix to a serine, while the rpoC2064 mutation duplicated positions 415 to 416 (valine-isoleucine) at the base of the β' dock domain. These findings support previously published in vitro results, which have suggested that the β' flap-tip helix and β' dock domain at either side of the RNA exit tunnel mediate the binding to NusA during transcriptional pausing and termination. © 2011, American Society for Microbiology.

Fei Y.Y.,University of California at Davis | Schmidt A.,Helicure AB | Bylund G.,Helicure AB | Johansson D.X.,Umea University | And 6 more authors.
Analytical Chemistry | Year: 2011

Infectious diseases are often initiated by microbial adherence that is mediated by the binding of attachment molecules, termed adhesins, to cell surface receptors on host cells. We present an experimental system, oblique-incidence reflectivity difference (OI-RD) microscopy, which allows the detection of novel, low-affinity microbial attachment mechanisms that may be essential for infectious processes. OI-RD microscopy was used to analyze direct binding of the oncopathogen, Helicobacter pylori (H. pylori) to immobilized glycoconjugates in real time with no need for labeling tags. The results suggest the presence of additional Lewis b blood group antigen (Le b) binding adhesins that have not been detected previously. OI-RD microscopy also confirmed the high-affinity binding of H. pylori outer-membrane protein BabA to Le b. The OI-RD microscopy method is broadly applicable to real-time characterization of intact microbial binding to host receptors and offers new strategies to elucidate the molecular interactions of infectious agents with human host cells. © 2011 American Chemical Society.

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