摘要:

SummaryStaphylococcus aureusstrains isolated from patients with septic arthritis or osteomyelitis possess a collagen receptor present in two forms, which contains either two or three copies of a 187‐amino‐acid repeat motif. Collagen receptor‐positive strains adhered to both collagen substrata and cartilage in a time‐dependent process. Collagen receptor‐specific antibodies blocked bacterial adherence, as did preincubation of the substrate with a recombinant form of the receptor protein. Furthermore, polystyrene beads coated with the collagen receptor bound collagen and attached to cartilage. Taken together, these results suggest that the collagen receptor is both necessary and sufficient to mediate bacterial adherence to cartilage in a process that constitutes an important part of the pathogenic mechanism in septic

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1993.tb01101.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe proteins KdpD and KdpE are crucial to the osmotic regulation of thekdpABCoperon that is responsible for the high‐affinity K+ion transport system inEscherichia coli.We demonstrated previously that the response regulator, KdpE, is capable of undergoing Phosphorylation mediated by the sensory protein kinase, KdpD. In this study, we obtained biochemical evidence supporting the view that when KdpE is phosphorylated, it takes on an active form that exhibits relatively high affinity for thekdpABCpromoter, which in turn results in activation of thekdpABCoperon. It was also suggested that the central hydrophobic domain of KdpD, which is conceivably responsible for membrane anchoring of this protein, plays a role in the signalling mechanism underlying KdpE Phosphorylation in response to hyperosmotic stres

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1993.tb01102.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryCatechol‐cephalosporins are siderophore‐like antibiotics which are taken up by cells ofPseudomonas putidaWCS358 via the ferric‐siderophore transport pathway. Mutants of strain WCS358 were isolated that are resistant to high concentrations of these antibiotics. These mutants failed to grow under iron‐limiting conditions, and could not utilize different ferric‐siderophores. The mutants fall in three complementation groups. The nucleotide sequence determination identified three contiguous open reading frames, which were homologous to theexbB, exbDandtonBgenes ofEscherichia colirespectively. The deduced amino acid sequence ofP. putidaExbB showed 58.6% homology with itsE. colihomologue, but, unlike theE. coliprotein, it has a N‐terminal extension of 91 amino acids. The ExbD proteins are 64.8% homologous, whereas the TonB proteins only show 27.7% homology. TheP. putida exbBgene could complement anE. coli exbBmutation, but the TonB proteins were not interchangeable between the species. It is concluded thatP. putidaWCS358 contains an energy‐coupling system between the membranes for active transport across the outer membrane, which is comprised of a TonB‐like energy‐transducing protein and two accessory proteins. This system is similar to, but not completely compatible with,

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1993.tb01103.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryA model for the topology of the PhoE porin has been proposed according to which the polypeptide traverses the outer membrane sixteen times mostly as amphipathic β‐sheets, thereby exposing eight loops at the cell surface. Until now, no evidence has been obtained for the surface exposure of the third loop. Recently, the structure of porin ofRhodobacter capsulatushas been determined. The proposed model of PhoE is very similar to the structure of the Rcapsulatusporin, which has an ‘eyelet’ region, extending into the interior of the pore. The proposed third external loop of PhoE might form a similar ‘eyelet’ region. To determine the location of the predicted third external loop of PhoE, multiple copies of an oligonucleotide linker encoding an antigenic determinant of VP1 protein of foot‐and‐mouth disease virus (FMDV) were inserted. All hybrid proteins were properly inserted in the outer membrane. The monoclonal antibody MA11, directed against the linear FMDV epitope, was able to bind only to intact cells expressing a hybrid PhoE protein with at least three copies of the FMDV epitope present. Antibiotic sensitivity tests and single‐channel conductance measurements revealed that the insertions influenced the channel size. These results are consistent with a location of the third loop of PhoE within

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1993.tb01104.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe presence of the α‐haemolysin secretion genes sensitizesEscherichia colito vancomycin, a glycopeptide antibiotic that is normally excluded from the Gram‐negative envelope (owing to its large size) (Mr1400). The selection of vancomycin mutants in strains carrying such genes was found to be a very powerful method for selecting non‐haemolytic mutants. In this way, mutations in the known secretion genes,hlyB, hlyDandtolC, were obtained. However additional mutations mapped in genesrfaHandgalUwhich are required for lipopolysaccharide (LPS) biosynthesis. Mutations inrfaHandgalUstrongly reduced α‐haemolysin secretion as weli as the secretion ofErwinia chrysanthemiproteases inE. coliwithout affecting their synthesis. These mutations markedly lowered the content of TolC protein, required for haemolysin secretion and also of the PrtF protein necessary for protease secretion. These results raise the possibility that LPS is involved in the correct incorporation of the TolC and PrtF proteins into the cell

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1993.tb01105.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryTranscription initiation at theEscherichia coli nirBpromoter is induced by anaerobic growth and further increased by the presence of nitrite or nitrate in the growth medium. Expression from this promoter is totally dependent on the transcription factor, FNR, which binds between positions −52 and −30 upstream of the transcription startsite. The 20 base pairs from position −79 to −60 contain an inverted repeat of two 10‐base sequence elements that are related to sequences at the NarL‐binding site at theE. coli narGpromoter. Comparison of these, and sequence elements at other promoters regulated by NarL, suggests a consensus NarL‐binding sequence. Mutations in the putative NarL‐binding site at thenirBpromoter decrease FNR‐dependent anaerobic induction, suggesting that NarL acts as a helper to FNR during transcription activation. These mutations also suppress induction by nitrite: single mutations at symmetry‐related positions have similar effects, whilst double mutations have more severe effects, probably because two NarL subunits bind to the inverted repeat. Disruption ofnarLdecreases nitrite induction of thenirBpromoter whilst not suppressing induction by nitrate, suggesting that there may be a second nitrate‐responsive factor. Nitrate induction was, however, suppressed by double mutations at symmetry‐related positions in the NarL‐binding site, suggesting that this putative second factor may bind to sequences similar to

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1993.tb01106.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY