摘要:

SummaryTherelFgene inEscherichia coliis related to thehokgene on plasmid R1. Both genes encode small proteins which, when overexpressed InE. colilead to collapse of the membrane potential and cell death. A third gene, designatedgef, which encodes a homologous cell‐toxic protein, has been isolated fromE. coliDNA. BothgefandrelFare transcribed inE. coliand subject to post‐transcriptional regulation which, in the case ofgef, is coupled to translation of a leader sequence. The finding of homologous sequences in such distantly related bacteria asAgrobacteriumandRhizobiumspecies suggests an important physiological r

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00131.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryPulsed‐field gel electrophoresis was used to generate a molecular karyotype of chromosomes from the opportunistic AIDS pathogen,Pneumocystis carinii. P. cariniicysts and trophozoites were isolated from immunosuppressed rats, lysedin situin agarose blocks, and subjected to orthogonal‐field gel electrophoresis (OFAGE) and contour‐clamped homogeneous‐field gel electrophoresis (CHEF). OFAGE and CHEF gels resolved, respectively, 16 or 20 chromosome bands ranging in size from 0.32‐1.5 megabase pairs. Summation of the estimated sizes of these chromosomes suggested a total genome complexity forP. cariniiof 8‐16 megabase pairs. Homologous probes for the genes encoding the 18S, 5.8S, and 5S ribosomal RNAs were hybridized to filter blots of the pulsed‐field gels to map these genes to specificP. carin

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryA gene that codes for a small stable RNA (362 nucleotides) has been sequenced. It is a monocistronic gene, with its own promoter and terminator. It produces a precursor that is about 100 nucleotides longer than the mature RNA with all the extra nucleotides at the 3′ end. The gene contains an open reading frame that corresponds to a small protein 25 amino acids lon

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryA DNA fragment encoding kanamycin resistance was insertedin vitrointo a plasmid‐borneprsgene encoding phosphoribosylpyrophosphate synthetase ofEscherichia coli.The resulting plasmids were subsequently transferred to the chromosome by homologous recombination and the haploid strainsprs‐3::KanRand prs‐4::KanRwere obtained. These strains were fully viable, but required guanosine, uridine, histidine, tryptophan and nicotinamide mononucleotide. There was no phosphoribosylpyrophosphate synthetase activity or phosphoribosylpyrophosphate pool in the mutant strains. These results show that phosphoribosytpyrophosphate synthetase is dispensable forE.

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00134.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe adherence of non‐mucoidPseudomonas aeruginosastrains is believed to be mediated by the pilus, which consists of a single protein subunit of 15000 Oaltons called pilin. Ten antipeptide antisera were raised to map the surface regions of pilin fromP. aeruginosastrain K (PAK). Only one of the antipeptide antisera to the eight predicted surface regions failed to react with PAK pili in direct ELISA. Five out of eight synthetic peptides representing the eight predicted surface regions reacted with anti‐PAK pilus anti‐serum, indicating their surface exposure. Combining the antipeptide and antipilus antisera results, all eight predicted surface regions were demonstrated to be surface‐exposed. The PAK 128‐144‐OH peptide produced the best binding antiserum to PAK pili. Only antipeptide Fab fragments directed against the disulphide bridged C‐terminal region of PAK piiin blocked the adherence of pili to human buccal epithelial cells, which suggests that this region contains the receptor‐binding domain o

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryAs a step towards indentifying exploitable differences between host and parasite at the molecular level, we have isolated and sequenced genomic clones encompassing an entire α‐tubulin gene (designated α‐tubulin I) from the human malaria parasite,Plasmodium falciparum.The gene, which contains two introns, encodes a product with a predicted length of 453 amino acid residues (50.3 kD). The protein sequence shows a high degree of homology to other α‐tubulins, particularly that of the coccidian parasite,Toxoplasma gondii(94%), whose gene carries introns in identical positions. Only one copy of the α‐tubulin I gene itself was found, although a second gene designated α‐II was also identified which is closely related but which differs at both the nucleotide and amino acid sequence levels. The α‐I and β‐tubulin genes were found to reside on d

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryWe describe the isolation and characterization of a gene for β‐tubulin from the malaria parasite,Plasmodium falciparum.This organism appears to contain a single gene encoding β‐tubulin. A single transcript from this gene can be detected in the total RNA of the parasite's asexual blood stages. The complete sequence for the gene has been elucidated. It has two introns, one of which has a position identical to that of a related parasite,Toxoplasma gondii.The gene shows the usual preference for codons with A or T in the third position. The predicted amino acid sequence is compared with that ofT. gondiiand the human host. Further comparisons between these and fungal sequences of β‐tubulins resistant to benomyl, a drug binding this protein, highlight differences that could be exploited in the development of parasite‐specific anti‐t

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTheEscherichia coli proUoperon encodes a high‐affinity, binding‐protein‐dependent transport system for the osmoprotectant glycine betaine. Expression ofproUis osmoregulated, and transcription of this operon is greatly increased In cells grown at high osmolarity. Characterization of theproUoperon and its promoter provided results similar to those published elsewhere (Gowrishankar, 1989; Stirlinget al., 1989). The previously identifiedproU601mutation, which leads to increasedproUexpression both at low‐and high osmolarity, is a G to A transition in the Pribnow box of theproUpromoter, which increases the homology of the ‐10 region to the consensus sequence ofE. colipromoters. Using an antiserum raised against a ProV‐β‐galactosidase hybrid protein, we have identified ProV as a protein associated with the cytoplasmic membrane. This cellular location is consistent with its proposed role as the energy ‐coupling component of the ProU

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe relative LD50values in two test Lepidoptera ofBacillus thuringiensissubspecieskurstaki HD1, which contains threecrylAprotoxin genes, was the same as a plasmid‐cured derivative or aBacillus cereustranscipient containing only one of the three genes. Differential rates of transcription of these genes in the original strain could account, at least partly, for this result. Strains containing only the single protoxin gene(crylA(b))produced inclusions when grown at 25°C but not 32°C, despite transcription of this gene at both temperatures. The instability of thecrylA(b)protoxin was not found in the parentalB. thuringiensissubsp.kurstakiHD1 strain grown at either temperature, however, sokurstakiHD1 strains with multiple protoxin genes must produce some stabilizing factor, perhaps another protoxin.Thecrylprotoxins contain a highly conserved carboxyl half which is proteolytically removed upon conversion to toxin. All of the protoxin cysteines are present in protease‐sensitive regions and they are oxidized in inclusions. Most of the disulphides appear to be essential for specificity since their reduction in thecrylA(b)protoxin resulted in loss of selectivity for one of the test insects. This lack of specificity was also found for this protoxin produced by anEscherichia coliclone, probably because of the reducing conditions in these cells. Specificity was restored by reoxidation of the pure protoxin, by removal of the carboxyl half of oxidized protoxin with trypsin, or by subcloning of the toxin portion. The oxidized form of protoxins must be important for specificity, for the formation of crystalline inclusions, and probably for interactions required for the stabilization of some prot

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTn21‐and Tn3‐related transposons are widespread and carry various resistance determinants. The insertion points of different resistance genes were precisely defined in Tn2424, Tn1696, Tn2410, Tn4000and its derivatives and compared to the corresponding sites in Tn7, pSA, R388, R46, Tn2603, Tn1331and in Tn3‐related elements. Insertional‘hot spots’located at the 3′ end of different genes comprised 55 nucleotides and yielded more than 90% homology to the corresponding consensus sequence, termed hs1. Elements of this class were found to directrecA‐independent generation of deletions. Flanking the 5’ends, hs2 (CTAAAACAAAGTTA) comprised the terminal nucleotides of hs1. Functional properties of hot spots as recognition sites for site‐specific recombination and regulation of gene expression indicate that they might be involved in transfer, stable inheritance and expression of

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1989.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY