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B Rak

Publications and source records attributed to B Rak.

27 records · Page 2Linked to original sources
PubMed1986

A 3.6-kbp segment from the vir region of Ti plasmids contains genes responsible for border-sequence-directed production of T region circles in E. coli.

The vir region of Ti plasmids is responsible for the transfer of the T region from Agrobacteria to plant cells; previous experiments suggested that formation of independent T region DNA circles is one step in this process. To study this step in Escherichia coli, we developed a binary vector system. One plasmid (= substrate) contains correctly oriented right and left borders from octopine plasmid pTiAch5. A gene with a counterselectable function (galK) was cloned between these borders. The galK gene is under control of the tac promoter-operator and the lac repressor with the laci gene also in the selection cassette. This construction allows determination of substrate plasmid mutants which have lost the selectable galK function. The second component of the system is one of a set of compatible plasmids harbouring various cloned parts from the vir region of nopaline plasmid pTiC58. A 3.6-kbp segment of the vir region turned out to be necessary and sufficient for production of substrate plasmid mutants which represented the equivalent of the T region containing a complete left border. From this vir region fragment four discrete proteins were expressed in minicells. The coding regions were mapped to a part conserved in nopaline and octopine plasmids; in the latter it appears to correspond to virC/D.

Cloning, Molecular↗
PubMed1984

Insertion element IS5 contains a third gene.

We have previously shown that IS5 contains two genes encoded on opposite DNA strands within the same stretch of DNA. Here we present evidence that a third gene and its promoter are present on IS5. The newly discovered gene, ins5C , is contained within the longest gene of IS5, ins5A , but encoded by the complementary DNA strand. The three genes comprise a total of 519 codons present on the 1195-bp element. The arrangement of these genes represents a coding structure of unprecedented compactness.

Codon↗
PubMed1983

Two site-specific endonucleases BinSI and BinSII from Bifidobacterium infantis.

Two site-specific endonucleases, BinSI and BinSII, were isolated from Bifidobacterium infantis S76e. BinSI was found to be an isoschizomer of EcoRII, while BinSII was shown to have the same sequence and cutting specificity as BbeI, 5'-GGCGC decreases C-3'. Both BinSII- and BbeI-generated DNA fragments could be ligated with HaeII-generated DNA fragments.

Base Sequence↗
PubMed1983

A control system which causes alternating turn-off/turn-on of transcription on insertion element IS1.

Presence of insertion element IS1 within an operon leads to absence of expression of genes distal to its integration site. This strong polar effect is observed irrespective of the orientation of IS1. Here I report on a mutant of E. coli K12 which allows turn-on of genes located distally to IS1. This turn-on is due to activation of transcription starting within IS1. The activation of transcription is under the control of a regulatory locus (sis1) which acts in trans. The regulatory locus itself changes its state, which leads to an alternating turn-off/turn-on of genes located distal to IS1: The rate of turn-off was observed with a frequency of about 0.3% (per cell and per generation), that of turn-on with a frequency of about 0.015% (per cell and per generation).

DNA Transposable Elements↗
PubMed1976

Gal mRNA initiated within IS2.

A strain of E. coli carrying IS2 in the control region of the gal operon has been found to revert to a constitutive phenotype. These revertants can be divided into two classes, which differ in their rate of enzyme synthesis and gal transcription. One revertant synthesizes the gal messenger at a low level (low level revertants), the other at a higher level that exceeds that of the induced wild type two- to three-fold (high level revertants). In both cases it has been shown that the gal messenger is covalently bound to IS2-RNA, which is transcribed from IS2 in the original orientation. The evidence suggests, that the section of the IS2-element, from which this RNA is transcribed in the case of the high level revertants is smaller than 50 nucleotides long: i.e. the resolution of the hybridization method used for the detection of sequence homologies exceeds that of the electron microscopical heteroduplex technique.

Coliphages↗