摘要:

SummaryA 71 kiloDalton antigen fromMycobacterium tuberculosisis recognized by antibodies and by T lymphocytes during infection (Brittonet al., 1986a). Partial sequence analysis indicates a relationship between this antigen and the highly conserved family of 70‐kiloDalton heat shock proteins (hsp70) (Younget al., 1988). Biochemical and serological characterization of the protein confirms its membership of the hsp70 gene family, and metabolic labelling demonstrates that it is a major component of the mycobacterial response to heat stress. The role of stress proteins as antigens during infection is discusse

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01801.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe class 1 protein is a major protein of the outer membrane ofNeisseria meningitidis, and an important immunodeterminant in humans. The complete nucleotide sequence for the structural gene of a class 1 protein has been determined. The sequence predicts a protein of 374 amino acids, preceded by a typical signal peptide of 19 residues. The hydropathy profile of the predicted protein sequence resembles that of theEscherichia coliand gonococcal porins. The predicted protein sequence of the class 1 protein exhibits considerable structural similarity to the gonococcal porins PIA and PIB. Western blot studies also reveal immunologically conserved domains between the class 1 protein, PIA and PIB. A restriction fragment from the class 1 gene hybridizes to gonococcal genomic fragments in Southern blots. In addition to the class 1 gene coding region there is a large open reading frame on the opposite strand.

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01802.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTheBradyrhizobfum japonicum fixXgene was identified and shown to be essential for symbiotic and free‐living, microaerobic nitrogen fixation. ThefixXgene encodes a ferredoxin‐like protein which may be Involved in a redox process (electron transport?) essential for nitrogenase activity. This gene was localized downstream offixCand its expression was dependent on thefixBpromoter, providing evidence for the existence of afixBCXoperon. Mutagenesis and sequence analysis of the unusually long, 709 bp leader region between thefixBpromoter and thefixBstructural gene did not reveal the presence of aniforfixgene that was absolutely essential for nitrogen fixation. However, a short open reading frame (ORF) within this region encoding a polypeptide of 35 amino acids (ORF35) was shown to be efficiently translated. Chromosomal deletion of a 400bp DNA fragment covering ORF35 resulted in a three‐fold reduction of thefixSCXmRNA level, which in turn also reduced the nitrogen fixation activity of this mutant. This suggests a possible post‐transcriptional control mechanism for the expression of thefixBCXoperon involving the stabilization offixBCXmRNA by ribosomes actively translatin

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01803.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe significance ofBradyrhizobium japonicumupstream activator sequences (UASs) for differential NifA‐mediatedfixandnifgene expression was investigated by two means: (i) hybridfixA‐andfixB‐lacZfusions were constructed by transposing anifH‐UAS cartridge in front of their promoters; and (ii)B. japonicummutants were generated carrying specific chromosomal deletions or UAS cartridge insertions within thefixA, fixBornifHpromoter‐upstream regions. Expression offixAwas not affected, and expression offixBdecreased only to 42%, when the respectivefixAandfixBpromoter‐upstream DNAs were deleted. This shows that inB. japonicumthe Njf A‐dependent activation of at least thefixApromoter does not require the presence of a closely adjacent UAS. Deletion of the UASs in front of thenifHgene not only reduced the expression ofnifHdown to 2.5% but, surprisingly, also resulted in a reduction of thefixBmRNA level to less than 20%. This suggests that thenifH‐UASs may exert a long‐range effect on the expression of the 3‐kb‐distantfixBCXoperon innifcluster I ofB. japonicum.Artificial transposition of thenif‐UASs in front of thefixAandfixBpromoters strongly enhanc

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01804.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTrimethoprim resistance mediated by theStaphylococcus aureusmulti‐resistance plasmid pSK1 is encoded by a structure with characteristics of a composite transposon which we have designated Tn4003.Nucleotide sequence analysis of Tn4003revealed it to be 4717 bp in length and to contain three copies of the insertion element IS257(789‐790 bp), the outside two of which are flanked by directly repeated 8‐bp target sequences. IS257has imperfect terminal inverted repeats of 27‐28 bp and encodes for a putative transposase with two potential α‐helix‐turn‐α‐helix DNA recognition motifs. IS257shares sequence similarities with members of the IS15family of insertion sequences from Gram‐negative bacteria and with ISS1fromStreptococcus lactis.The central region of the transposon contains thedfrAgene that specifies the S1 dihydrofolate reductase (DHFR) responsible for trimethoprim resistance. The S1 enzyme shows sequence homology with type I and V trimethoprim‐resistant DHFRs from Gram‐negative bacteria and with chromosomally encoded DHFRs from Gram‐positive and Gram‐negative bacteria. 5’todfrAis a thymidylate sy

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01805.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe UDP‐sugar hydrolase ofSalmonella typhimuriumhas previously been reported to be located in both the inner and the outer membrane. We have cloned the gene, designatedushB, encoding this enzyme and determined its nucleotide sequence. No significant sequence homology with the periplasmic UDP‐sugar hydrolase ofEscherichia coliwas found at either the DNA or protein level. However, a sequence is detectable, in theE. coligenome, which weakly hybridizes with a specificushBprobe. Polypeptide analysis has allowed the identification of theSalmonellahydrolase which has anMrof 28349 as compared to anMrof 60767 for theE. colihydrolase. Most of the protein (∼90%) is located in the inner membrane. Two independent membrane fractionation procedures indicate that the remainder may be associated with the outer membrane. The deduced primary structure indicates the presence of anN‐terminal signal peptide, although certain features of the region surrounding the putative processing site indicate that processing may be inefficient, or may not occur. Experiments with several inhibitors of signal peptidase function fail to demonstrate the appearance of a precurs

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01806.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThefdhFgene, encoding the selenopolypeptide of formate dehydrogenase (FDHH). has a ‐12/‐24nif‐type consensus promoter. Acis‐acting DNA element, which is required for the regulation of the promoter by formate under anaerobic conditions, has been identified. This regulatory sequence of about 25bp in length is located 110 bp upstream of the transcription start site. By analysing a variety of mutant constructs in this region (5’deletions, internal deletions and point mutations) we were able to identify a hexanucleotide sequence ‐GTCACG‐, which is important for the formate regulation of thefdhFpromoter. The data also indicate that this element has many of the properties characteristic of eukaryo

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01807.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe gene specifying the group A streptokinase (ska) gene was cloned from an M type 49 strain ofStreptococcus pyogenesand shown to express inEscherichia coli.The nucleotide sequence of the DNA fragment carryingskawas determined and compared to that of the group C streptokinase gene (skc). There is 90% sequence identity between the two genes, with highly conserved transcription and translation control regions. The deduced amino acid sequence of the group A streptokinase (SKA) contains the same number of amino acids as that of group C streptokinase, with 85% sequence identity between the two proteins. Among 440 amino acid residues specified by the coding sequence, there are 62 non‐identical residues with 45 conserved and 17 non‐conserved residues. The non‐identical residues are located in two major regions, spanning residues 174 to 244 and 270 to 290, with 40 and 10 amino acid changes, respectively. The sequence differences provide an explanation at the molecular level for the previous findings of immunological and chemical heterogeneity among streptokinases produced by pathogenic strepto

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01808.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryInShigella flexneri, in addition to several well‐recognized plasmid‐borne virulence loci, at least three genetic loci implicated in pathogenesis have been recognized on the chromosome. To understand more about the pathogenesis of bacillary dysentery at a molecular level, the genetically recognized but previously unidentified KcpA region (one of the chromosomal regions nearpurE) was cloned and sequenced. A single translatable open reading frame encoding a 12310 Dalton protein corresponding to the minicell product was found. Immunofluorescence microscopy, as well as optical and electron microscopic comparison of tissue‐cultured cells and guinea‐pigs’eyes infected with wild‐type orkcpAmutant bacteria, revealed that thekcpAproduct is required by invading bacteria for spread into adj

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01809.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe synthesis of heat‐shock proteins can be triggered by a variety of stress‐inducing conditions. Here we show that translational misreading caused by growth in the presence of the aminoglycoside antibiotic paromomycin will induce the heat‐shock response in the yeastSaccharomyces cerevisiae.This was demonstrated (i) by the acquisition of thermotolerance, and (ii) by elevated levels of expression of the heat‐shock protein, hsp70. In addition, transcription of the ubiquitin gene (UBI4) was increased in paromomycin‐grown cells. Control experiments with the protein synthesis inhibitor cycloheximide (which does not induce translational misreading) demonstrated that the response was not due to inhibition of protein synthesisper se.These observations strongly suggest that the synthesis of abnormally high levels of aberrant proteins is the trigger of the heat‐shock response in this simpl

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb01810.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY