摘要:

SummaryThe mini‐circle is a transposable element which is present inStreptomyces coelicolorA3(2) in both free circular and chromosomally integrated linear forms. The nucleotide sequences of the mini‐circle and its preferred site of integration in theStreptomyces lividansTK64 chromosome were determined. Three putative open reading frames were identified in the mini‐circle sequence. The mini‐circle does not appear to cause a target site duplication on transposition and does not have perfect terminal inverted repeats. The observed site‐specificity of the mini‐circle is not mediated by extensive homology between the element and the chromosomal integration site. Transposition of the mini‐circle into theS. lividanschromosome was demonstrated and found to be some two orders of magnitude less efficient than integration of the circular form of the element, suggesting that the circular form of the mini‐circle might be a normal intermediate in the transp

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00112.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTheNSP1 gene inSaccharomyces cerevisiaehas been identified by its ability, when expressed at high levels, to bypass theCDC25 requirement for growth. Sequence analysis of the clonedNSP1 locus suggests that theNSP1 product contains 269 amino acids and has a membrane‐spanning domain at its carboxyl terminus. TheNSP1 protein does not have sequence similarity to other known proteins, and is not related to theCDC25 protein, or to any of the previously described suppressors ofCDC25 mutants. Phosphoprotein analysis ofNSP1‐suppressed cells indicates that theNSP1 product controls the phosphorylation of two 31 kD proteins whose phosphorylation and de‐phosphorylation are strongly correlated with cell‐cycle arrest and proliferation, respectively, and suggests that theNSP1 product is an important downstream element of aCDC25‐dependent, nutrient‐responsive, phosphorylat

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00113.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryMorphological evidence has previously indicated that the periplasmic space ofEscherichia coliis compartmentalized at sites corresponding to future sites of cell division. The borders of these morphological compartments are formed by localized zones of adhesion (periseptal annuli). In the present study, the technique of fluorescence recovery after photo‐bleaching was used to determine whether these structures act as barriers to the free movement of proteins within the periplasm. The recovery of fluorescence in theftsAfilaments was found to be uniformly low over at potential sites of cell division and at the cell poles, indicating that these regions are biochemically sequestered from the remainder of the periplasmic space. Our results provide direct evidence for local compartments within the periplasm, primarily located at the sites of past or future cell divisions. The implications of this finding for cell division and other periplasmic processes are discusse

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00114.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryDevelopment of penicillin resistance inStreptococcus pneumoniaeis due to successive mutations in penicillin‐binding proteins (PBPs) which reduce their affinity for β‐lactam antibiotics. PBP2x is one of the high‐MrPBPs which appears to be altered both in resistant clinical isolates, and in cefotaxime‐resistant laboratory mutants. In this study, we have sequenced a 2564 base‐pair chromosomal fragment from the penicillin‐sensitiveS. pneumoniaestrain R6, which contains the PBP2x gene. Within this fragment, a 2250 base‐pair open reading frame was found which coded for a protein having an Mrof 82.35 kD, a value which is in good agreement with the Mrof 80–85kD measured by SDS‐gel electrophoresis of the PBP2x protein itself. The N‐terminal region resembled an unprocessed signal peptide and was followed by a hydrophobic sequence that may be responsible for membrane attachment of PBP2x. The corresponding nucleotide sequence of the PBP2x gene from C504, a cefotaxime‐resistant laboratory mutant obtained after five selection steps, contained three nucleotide substitutions, causing three amino acid alterations within the β‐lactam binding domain of the PBP2x protein. Alterations affecting similar regions ofEscherichia coliPBP3 andNeisseria gonorrhoeaePBP2 from β‐lactam‐resistant strains are known. The penicillin‐binding domain of PBP2x shows highest homology with these two PBPs andS. pneumoniaePBP2b. In contrast, theN‐terminal extension of PBP2x has the highest homology withE. coliPBP2 and methicillin‐resistantStaphylococcus aureusPBP2′. No significant homology was detected with PBP1a or PBP1b ofEs

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00115.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryInKiebsiella pneumoniae, the mucoid phenotype, which is a virulence factor, is distinct from capsule production. It is positively controlled by a plasmid gene, designatedrmpA.When introduced into certainEscherichia colistrains,rmpAinduces expression of a mucoid phenotype, which results from overproduction of colanic acid at 30° C but not at 37°C. InE. coli, production of colanic acid is regulated by three genes:rcsAandrcsBwhich act as positive regulators, andrcsCwhich is a negative effector. In this work we present evidence that thermpAgene complemented anrcsA, Iondouble mutant ofE. coli, but not anrcsA, ion+isolate. This leads to the suggestion thatrmpAexpressed anrcsA‐like activity and likercsA, was negatively controlled at post‐transcriptional level by the Lon protease. The nucleotide sequence ofrmpAis reported. No homology could be found between the 27 kiloDalton RcsA protein and the deduced amino acid sequence of the 15.5 kiloDalton RmpA protein. Another gene,rmpB, which was required inE. coli recAisolates for full expression ofrmpAat 30° C, has been identified on theK. pneumoniaevirulence plasmid and shown to encode a 37 kiloDalton protein. AlthoughrmpBwas closely linked tormpA, it was not present on the same transcriptional unit. These results suggested that induction of colanic acid synthesis by theK. pneumoniaevirulence genermpA, was, at least inE. coli, under the control of the RecA network viarmpB, which may act as a positive regulator ofrmpA.We conclude that these plasmid genes may function inK. pneumoniaeas regulatory genes controlling the mucoid phenotype, which is itself encoded by the chro

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00116.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryA plasmid vector, pYZ1, was constructed which lacks most of the β‐lactamase signal‐peptide coding region, but has a uniqueEcoRI site spanning codons 2 and 3 of the resultant cytoplasmic β‐lactamase derivative. Short quasi‐random DNA sequences were cloned into theEcoRI site andEscherichia colitransformants in which some translocation of β‐lactamase across the cytoplasmic membrane was restored were selected by their ability to survive and form colonies on plates containing a low level of ampicillin. About 15–20% of all in‐frame inserts restored some β‐lactamase trans‐location and the salient feature of these sequences was their marked hydrophobicity. These results are discussed in the light of a similar study in which sequences able to function as translocators of invertase in yeast were cloned and analysed

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00117.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe completeEscherichia coli ftsQcoding sequence, together with part of theftsAcoding sequence, has been cloned upstream of thelacZopen reading frame in a λ‐vector (λJFL100). Cells which are lysogenic for λJFL100 transcribe the clonedlacZfrom promoter(s) within theftsQandftsAsequences. The level of β‐galactosidase produced is dependent on growth rate (and/or cell size) and Is derepressed in anftsA‐deficient mutant. Transcription during the cell cycle is restricted to the time of cell

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00118.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTheHI(now renamedfliC; linoet al., 1988) alleles specifying antigenically differentSalmonellaflagellins are identical at their ends but differ greatly towards the middle, where there are two hypervariable segments (regions IV and VI). The flagellar antigen,d, ofSalmonella typhi, is found also as phase‐1 antigen in many otherSaimonellaspecies. We cloned theH1‐dgene of a strain ofS. typhiand determined the nucleotide sequence of its two hypervariable regions. Comparison with geneH1‐dofSalmonella muenchenshowed substantial differences in region VI: four scattered amino acid differences and ten adjacent amino acids in the inferredS. typhisequence, all of which differ from the corresponding nine amino acids in theS. muenchensequence. The results of polymerase chain reaction amplification indicated the presence of theS. typhiversion in all of 18 additionalS. typhistrains and the presence of theS. muenchenversion in all four non‐S. typhispecies with flagellar antigend. The difference in amino acid sequence in segment VI may be responsible for the minor serological differences between antigens d ofS. typhiand antigendofS. m

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00119.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTranscriptional regulation of thedeoP2 promoter by the cyclic AMP/cyclic AMP receptor protein complex (cAMP/CRP) and the CytR repressor requires two high‐affinity CRP targets located around ‐41 and ‐93 bp preceding the start site for transcription. Here we report the structure ofcddP, another CRP/CytR‐regulated promoter. In common with what was found indeo, thecddpromoter also contains multiple CRP targets. Thus, using the DNasel footprinting procedure, tandem CRP binding sites were identified around ‐41 and ‐93. These findings support a general model for CytR binding and CytR regulation, in which (i) CytR and the CRP/cAMP complex bind to similar or Identical targets, (ii) two or more targets are necessary for proper binding of CytR to a promoter region, and (iii) CytR represses transcription by antagonizing cAMP/CRP

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00120.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe structural gene for deoxyguanosine triphosphate triphosphohydrolase (dGTPase) (EC 3.1.5.1) and its regulator,optA, have been located on a lambda phage carrying a 17.5kbEscherichia coliDNA insert. The DNA fragment has been excised and ligated into pBR325 and also transferred to another lambda vector. From the results of transduction and transformation experiments, we find that the structural gene for dGTPase is very closely linked tooptAanddapD, which locates it at approximately 3.6 minutes on the genetic map ofE. coliK12. We propose the mnemonicdgtas the designation for the structural gene for this enzyme.

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00121.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY