Biomedical subjects

Sonja Oehmcke

Publications and source records attributed to Sonja Oehmcke.

4 recordsLinked to original sources

PubMed2006

Transcription of the pst operon of Clostridium acetobutylicum is dependent on phosphate concentration and pH.

The pst operon of Clostridium acetobutylicum ATCC 824 comprises five genes, pstS, pstC, pstA, pstB, and phoU, and shows a gene architecture identical to that of Escherichia coli. Deduced proteins are predicted to represent a high-affinity phosphate-specific ABC (ATP-binding cassette) transport system (Pst) and a protein homologous to PhoU, a negative phosphate regulon regulator. We analyzed the expression patterns of the pst operon in P(i)-limited chemostat cultures during acid production at pH 5.8 or solvent production at pH 4.5 and in response to P(i) pulses. Specific mRNA transcripts were found only when external P(i) concentrations had dropped below 0.2 mM. Two specific transcripts were detected, a 4.7-kb polycistronic mRNA spanning the whole operon and a quantitatively dominating 1.2-kb mRNA representing the first gene, pstS. The mRNA levels clearly differed depending on the external pH. The amounts of the full-length mRNA detected were about two times higher at pH 5.8 than at pH 4.5. The level of pstS mRNA increased by a factor of at least 8 at pH 5.8 compared to pH 4.5 results. Primer extension experiments revealed only one putative transcription start point 80 nucleotides upstream of pstS. Thus, additional regulatory sites are proposed in the promoter region, integrating two different extracellular signals, namely, depletion of inorganic phosphate and the pH of the environment. After phosphate pulses were applied to a phosphate-limited chemostat we observed faster phosphate consumption at pH 5.8 than at pH 4.5, although higher optical densities were recorded at pH 4.5.

Base Sequence↗

PubMed2005

Streptococcus pyogenes collagen type I-binding Cpa surface protein. Expression profile, binding characteristics, biological functions, and potential clinical impact.

The Streptococcus pyogenes collagen type I-binding protein Cpa (collagen-binding protein of group A streptococci) expressed by 28 serotypes of group A streptococci has been extensively characterized at the gene and protein levels. Evidence for three distinct families of cpa genes was found, all of which shared a common sequence encoding a 60-amino acid domain that accounted for selective binding to type I collagen. Surface plasmon resonance-based affinity measurements and functional studies indicated that the expression of Cpa was consistent with an attachment role for bacteria to tissue containing collagen type I. A cpa mutant displayed a significantly decreased internalization rate when incubated with HEp-2 cells but had no effect on the host cell viability. By utilizing serum from patients with a positive titer for streptolysin/DNase antibody, an increased anti-Cpa antibody titer was noted for patients with a clinical history of arthritis or osteomyelitis. Taken together, these results suggest Cpa may be a relevant matrix adhesin contributing to the pathogenesis of S. pyogenes infection of bones and joints.

Amino Acid Sequence↗

PubMed2004

Streptococcus pyogenes fibronectin-binding protein F2: expression profile, binding characteristics, and impact on eukaryotic cell interactions.

Some Streptococcus pyogenes (group A streptococci, GAS) strains have previously been shown to express the fibronectin-binding protein F2 instead of the functionally related but structurally dissimilar protein F1/SfbI. In this study, recombinant N-terminal and C-terminal portions and the two fibronectin-binding domains of protein F2 were used to assess affinity parameters of the interaction with fibronectin and its N-terminal 70-, 30-, and 45-kDa fragments. The association and dissociation equilibrium constants for both binding domains were in the nanomolar range, although the repeat domain of protein F2 exceeded the affinity of the unique domain by up to one order magnitude. Both domains primarily interacted with the 30-kDa fibronectin fragment. Using a prtF2 gene isogenic mutant of a serotype M49 GAS strain that does not harbor the protein F1/SfbI gene, the attachment values of whole bacteria to immobilized fibronectin and to HEp-2 epithelial cells were found to be 6- and 2-fold decreased, respectively. Reduction of prtF2 mutant internalization rates for eukaryotic cells exceeded the reduction of attachment rates, indicating an independent contribution of protein F2 to both processes. The prtF2 transcription and protein F2 expression profiles documented maximum expression at the transition to the stationary phase especially under aerobic growth condition. The protein F2 function as the major fibronectin-binding adhesin in a subset of GAS strains, its expression pattern, and highly specific interaction with fibronectin would be consistent with a status as an indispensable virulence factor for both earlier and later pathogenetic stages of GAS superficial infections.

Adhesins, Bacterial↗

PubMed2004

Function of the fibronectin-binding serum opacity factor of Streptococcus pyogenes in adherence to epithelial cells.

The serum opacity factor (SOF) of Streptococcus pyogenes is a serotyping tool and pathogenesis factor. Using SOF-coated latex beads in cell adherence assays and antiserum directed against SOF in S. pyogenes-HEp-2 cell adherence inhibition experiments, we demonstrate SOF involvement in the fibronectin-mediated adherence of S. pyogenes to epithelial cells. SOF exclusively targets the 30-kDa N-terminal region of fibronectin. The interaction revealed association and dissociation constants 1 order of magnitude lower than those of other S. pyogenes fibronectin-binding proteins.

Binding Sites↗