摘要:

SummaryProtein import into mitochondria involves a number of complex steps occurring in the cytosol, on the mitochondrial surface, and inside the organelle. Once an initial interaction between mitochondrial proteins and their specific receptors occurs, the proteins are transported into the organelle in a series of reactions involving (in the case of a protein to be translocated into the mitochondrial matrix) the mitochondrial membrane potential, ATP hydrolysis and an undetermined number of membrane components. Inside the organelle, mitochondrial proteins are processed and sorted to their final intramitochondrial destinations. The earliest steps in the import process take place in the cytosol and include the synthesis of the mitochondrial proteins themselves, their interaction with cytosolic factors, and perhaps the establishment of cotranslational import complexes on the mitochondrial surface. These early events are important because it is during this phase that the system as a whole is most sensitive to cytosolic conditions that may exert control over the entire import process.

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01344.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryInteractions of human neutrophils with recombinantEscherichia coliexpressing gonococcal outer membrane Opa proteins were examined using chemiluminescent and biological assays. Sevenopaloci fromNeisseria gonorrhoeaeMS11 4.8 were expressed as β‐lactamase‐Opa fusion proteins that contained all but the matureN‐terminal amino acid of the full‐length Opa protein fused to threeN‐terminal amino acids derived from the mature β‐lactamase. The Opa fusion proteins were exported and assembled in the outer membrane ofE. coliin a manner similar to that of Opa inN. gonorrhoeae, as evaluated by antibody binding andin situproteolytic cleavage. All fusion proteins exhibited the characteristic heat‐modifiable migration in SDS‐polyacrylamide gel electrophoresis that typifies Opa proteins of neisseriae. Opa fusion proteins conferred onE. colithe ability to stimulate a chemiluminescent response from human neutrophils in the absence of antibody or complement. The nature of the response in terms of chemiluminescence, phagocytosis, and killing was in all cases analogous to that seen usingN. gonorrhoeaeexpressing the equivalent Opa protein. NeitherE. colinor gonococci expressing OpaA elicited a response from neutrophils. Use ofE. coliexpressing Opa fusions should be useful in defining their biological activities and

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01345.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryLysyl‐tRNA synthetases are synthesized inEscherichia colifrom two distinct genes,lysSandlysU, which are regulated differentially. A strain which is null forlysS, the constitutive gene, was created by gene disruption (lysS1) and exhibited cold‐sensitive lethality. Hence,lysSis dispensable at high temperatures. This cold sensitivity was suppressed by a multi‐copy plasmid carryinglysU, the inducible gene. These data are interpreted as indicating thatlysSis functionally replaceable bylysUfor cell growth, and that the cold sensitivity oflysS1is caused by insufficient expression oflysUat low temperatures. To investigate the mechanism oflysUexpression, cold‐resistant bypass mutations were isolated fromlysS1, and named als (for abandonment oflysS.). Twoalsmutations which were linked tolysUcontain IS2insertions upstream of thelysUpromoter. They caused a 16–19‐fold increase in thelysU‐mRNA level. Furthermore, deletion mutations created immediately upstream of thelysUpromoter restored growth oflysS1.These results suggest that transcription oflysUis negatively controlled by acis‐element located upstream

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01346.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThreeAcinetobacter calcoaceticustransformation‐deficient mutants, obtained by insertional mutagenesis with thenptIIgene, have been characterized physiologically. One mutant (AAC211) was found to be completely transformation deficient, while two others, AAC213 and AAC214, were severely impaired in transformation efficiency (100–1000 times lower than the wild type). The latter applied to both chromosomal as well as plasmid DNA. Analysis of the chromosomal DNA fragments flanking thenptllgene in the mutants showed that mutants AAC213 and AAC214 had an insertion of thenptll genein the same chromosomal region, but that they were the result of two independent mutational events, whereas the insertion in mutant AAC211 was at a different position. None of the three mutants showed phenotypic or genotypic characteristics typical of a RecA‐deficient s

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01347.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe genes coding for the binding‐protein‐dependent lactose transport system and β‐galactosidase inAgrobacterium radiobacterstrain AR50 were cloned and partially sequenced. A novellacoperon was identified which contains genes coding for a lactose‐binding protein (lacE), two integral membrane proteins (lacFandlacG), an ATP‐binding protein (lacK) and β‐galactosidase (lacZ). The operon is transcribed in the orderlacEFGZK, The operon is controlled by an upstream regulatory region containing putative ‐35 and ‐10 promoter sites, an operator site, a CRP‐binding site probably mediating catabolite repression by glucose and galactose, and a regulatory gene (lacl) encoding a repressor protein which mediates induction by lactose and other galactosides in wild‐typeA. radiobacter(but not in strain AR50, thus allowing constitutive expression of thelacoperon). The derived amino acid sequences of the gene products indicate marked similarities with other binding‐protein‐dependent tran

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01348.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryExpression of theEscherichia coli kdpABCoperon, which is responsible for a high‐affinity potassium‐uptake system, is regulated in response to a change in the medium osmolarity. In this study, we clarified the structure and function of thekdpABCpromoter including its regulatory sequence at the molecular level. The canonical ‐35 and ‐10 regions determined for the promoter were not fully functional, i.e. in addition to them, acis‐acting sequence located upstream of the ‐35 region was essential for full activation of the promoter. This upstream sequence was demonstrated to be the target site for thetrans‐acting ac

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01349.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe proteins KdpD and KdpE are regulatory factors critically involved in the osmotic regulation of thekdpABCoperon that is responsible for a high‐affinity transport system inEscherichia coli.In this study, we obtained biochemical evidence supporting the view that the KdpD protein is a sensory protein kinase that exhibits autophosphorylation and KdpE‐phosphotransfer characteristics. During the course of such studies we established a procedure for purifying the KdpE protein in large quantities. We also developed a procedure for preparing cytoplasmic membrane enriched with the KdpD protein that exhibitsin vitroability with regard to phosphorylation of KdpE prot

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01350.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryA 2.6kb plasmid, named pBBR1, was isolated fromBordetella bronchisepticaS87. After insertion of an antibiotic resistance marker, this plasmid could be transferred intoEscherichia coli, Bordetella pertussis, B. bronchiseptica, Vibrio cholerae, Rhizobium meliloti, andPseudomonas putidaby transformation or conjugation. Conjugation was possible only when the IncP group transfer functions were providedin trans.As shown by incompatibility testing, pBBR1 does not belong to the broad‐host‐range IncP, IncQ or IncW groups. DNA sequence analysis revealed two open reading frames: one was called Rep, involved in replication of the plasmid, and the other, called Mob, was involved in mobilization. Both the amino‐termtnal region of Mob and its promoter region show sequence similarities to Mob/Pre proteins from plasmids of Gram‐positive bacteria. In spite of these sequence similarities, pBBR1 does not replicate via the rolling‐circle mechanism commonly used by small Gram‐positive plasmids. We therefore speculate that pBBR1 may combine a mobilization mechanism of Gram‐positive organisms with a replication mechanism of Gram‐negative organisms. Determination of the plasmid copy number inE. coliandB. pertussisindicated that pBBR1 has a rather high copy number, which, in conjunction with its small size and broad host range, renders it paricularly interesting for studies of broad‐host‐range replicons and for the development of new cloning vectors for a wide range of Gra

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01351.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryBacillary angiomatosis (BA) and chronic bartonellosis are bacterial infections of humans which result in an unusual vascular proliferative tissue response. In order to determine their phylogenetic relationships, we have determined greater than 95% of the 16S rRNA sequences for these two organisms by amplification directly from infected BA tissue and from aBartonella bacilliformislyophilized culture. The BA agent andB. bacilliformisare closely related alpha‐proteobacteria (98.5%), although the BA agent is more closely related toRochalimaea quintana(99.1%). Contrary to previous belief, the BA agent is distinct from, and less closely related to, the cat scratch bacillus (Afipia fells) (90.7%). We propose a novel secondary structure in a hypervariable region of the 16S rRNA which is useful for alignment of primary sequences and which may be useful for design of nucleic acid probe

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01352.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThed,l‐nicotine catabolism of the Gram‐positive soil bacteriumArthrobacter oxidansis linked to the presence within the cells of the 160 kb catabolic plasmid pAO1. pAO1‐cured cells lost the catabolic enzymes and reintroduction of pAO1 by electroporation into cured cells reestablished thenic+phenotype. DNA band shift assays with extracts from cured and pAO1+cells suggested that pAO1 encodes the regulatory protein NicR1. Footprint analysis revealed that two homologous palindromes (IR1 and IR2), present in the 5′‐regulatory region of the 6‐HDNO gene, were protected from DNase I digestion. Binding of NicR1 to the palindromes is symmetrical, co‐operative, and stronger to IR1 containing the 6‐HDNO gene promoter than to IR2. Site‐directed mutagenesis revealed that steric constraints and sequence requirements for NicR1 ‐binding are located exclusively in the palindromic sequences. Deletions and insertions in the interpalindromic region and in the 6‐HDNO promoter ‐10 sequence had no effect on the binding characteristics of NicR1 to the 6‐HDNO regulatory region. Acting as a repressor, NicR1 prevents binding of theE. coliRNA‐polymerase to the consensus σ70promoterin vitro.However, the Interaction of NicR1 with the 6‐HDNO promoter region in extracts of nicotine‐induced cells from various growth stages did not differ from that observed with extr

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1992.tb01353.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY