摘要:

SummaryPhycobilisomes are the major constituents of the light‐harvesting apparatus in both cyanobacteria and red algae and consist of a central core with radiating rods. From a genomic library of the cyanobacteriumCalothrix7601, a DNA fragment encoding allophycocyanin B, one of the two terminal energy acceptors of the core, was isolated and its nucleotide sequence was determined. Unlike all the other known genes encoding phycobiliproteins, the allophycocyanin B gene,apcD, is transcribed as a monocistronic unit. Mapping of the transcripts was performed and, in contrast to some of theCalothrixgenes that encode rod components, transcription was shown to occur regardless of chromatic tight received during cell growt

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00011.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryDominant mutations of the cet gene ofEscherichia coliresult in tolerance to colicin E2 and increased amounts of an inner membrane protein with an Mrof 42 000. We have cloned the cet+gene and sequenced its DNA, revealing that the gene product, coded by the longest open‐reading frame, has an Mrof 49772, with five predicted transmembrane structures towards its carboxy terminus and one at its amino terminus. We have demonstrated that the cet locus does in fact code for the inner membrane protein that is present in increased amounts in cet mutants, and we have shown that this increased amount of Cet protein is the result of enhanced transcription. The cet gene is shown to be in the same operon as thephoMgene, which is required in aphoRbackground for expression of the structural gene for alkaline phosphatase,phoA.Although the Cet protein is not required forphoAexpression, our experiments suggest that the Cet protein has an enhancing effect on the transcription ofphoA.No effect of phosphate concentration on cet orphoMgene expression could be found and thus their primary function may not be connected to the phosphate regulo

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00012.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe DNA sequence of the structural gene (yopE) of one of theYersinia pseudotuberculosisvirulence plas‐mid‐plB1‐encoded proteins, Yop5, is presented. The deduced protein showed a molecular weight of 22971 Daltons. A specific mutant, having a kanamycin‐resistance fragment inserted within theyopEgene was no longer virulent for mice. The expression of the Yop5 protein is regulated at the level of transcription by temperature as well as by the Ca2+‐concentration of the medium. A significant increase in the level of transcription was not detected until 45 min after a temperature shift from 26°C to 37°C in the absence of calcium; addition of Ca2+inhibited the expression. TheyopEpromoter is under positive, as well as negative, plB1‐encoded control. The positive function is solely regulated by temperature, while the regulation of the negative function involves at least five different plasmid‐encoded gene loci; one of these genes encode

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00013.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummarySpontaneous mutants ofStreptococcus mutansGS‐5 defective in sucrose‐dependent colonization of smooth surfaces are generated at frequencies above the spontaneous mutation rate. Southern blot analysis of such mutants suggested rearrangement of the genes coding for glucosyltransferase (GTF) activity. Two strain GS‐5 homologous tandem genes,gtfBandgtfC, coding for GTF‐I and GTF‐S activities respectively, were demonstrated to undergo recombination when introduced into recombination‐proficientEscherichia colitransformants. However, the two genes were quite stable when transformed on a single DNA fragment into arecAmutant ofE. coli.The DNA fragment coding for GTF activity from oneS. mutanscolonization‐defective mutant, SP2, was isolated and shown also to have undergone recombination between thegtfBandgtfCgenes, resulting in reduced GTF activity. These results are discussed relative to thein vivogeneration of colonization‐defective mutants in cultur

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00014.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe high‐affinity histidine permease ofSalmonella typhimuriumis encoded by a four‐gene operon containing a large intercistronic region located between the first gene (hisJ) and the three distal genes (hisQ, hisM, hisP). The level of expression ofhisJis 30‐fold greater than that ofhisP.In order to investigate the role of the intercistronic region in intra‐operonic control of gene expression, we have isoiatedMudII‐mediatedIacZgene fusions tohisQ, hisMandhisP.We have used these fusions to isolate and analyse mutants that have altered levels of expression of thehisQgene, the first gene downstream from the intercistronic region. The results indicate that intra‐operonic regulation is due to a combination of factors including efficiency of translational initiation, mRNA degradation, and retroregulation ofhisJexpression. They also suggest that the REP (RepetitiveExtragenicPalin‐dromic) sequences, which are located in thehisJ‐hisQintercistronic region, may interfere with translation of thehisQgene and affect upstream messenger RNA stability by protecting it from 3’to 5’nuclease degradation (in agreement with data presented by N

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00015.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryBacillus thuringlensisvar.aizawaiHD–249 produces more than one protein of 130–135 kD in its insecticidal crystal δ‐endotoxin. We describe an indirect method of assessing the relative contribution to toxicity of two of these protoxins using monospecific antibodies directed against their active proteolytic products. Our results show that one toxin is active againstSpodoptera frugiperdabut notChoristoneura fumiferanacellsin vitro, while the other lyses C.fumiferanabut notS. frugiperdacells. There is no indication of synergism between these toxinsin

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00016.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryNucleotide sequencing of thecelZgene encoding the extracellular endoglucanase Z ofErwinia chrysanthemiindicated the presence of an open reading frame encoding 428 amino acids. The mature protein appeared to be extended by a signal peptide of 43 amino acids; this sequence is unusually long and positively charged (+5). It was shown to function as a signal peptide by fusing it to a truncatedphoAgene encodingEscherichia colialkaline phosphatase. Comparison of the encoded sequence with those of the endoglucanases ofBacillus subtilisand alkalophilicBacillusrevealed the existence of a region of extensive homology occurring in all three proteins at about the same distance from the NH2‐terminal end. These regions may be involved in substrate binding and/or catalytic site

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1988.tb00017.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY