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PubMedDate not supplied

[Affinity modification of DNA-dependent RNA-polymerase from phage T7 with 5'-p-fluorosulfonylbenzoyl adenosine: the effect of modification on the interaction with substrates].

T7 RNA polymerase, covalently modified with 5'-p-fluorosulfonylbenzoyl adenosine, looses the ability of binding the promoter (pGEM-2 plasmid) and poly(dC) template as well as the initiating nucleoside triphosphate (GTP). However the enzyme retains the unspecific binding with DNA fragments of considerable length.

Adenosine↗
PubMed1989

The fokI restriction-modification system. I. Organization and nucleotide sequences of the restriction and modification genes.

A DNA fragment that carried the genes coding for FokI endonuclease and methylase was cloned from the chromosomal DNA of Flavobacterium okeanokoites, and the coding regions were assigned to the nucleotide sequence by deletion analysis. The methylase gene was 1,941 base pairs (bp) long, corresponding to a protein of 647 amino acid residues (Mr = 75,622), and the endonuclease gene was 1,749 bp long, corresponding to a protein of 583 amino acid residues (Mr = 66,216). The assignment of the methylase gene was further confirmed by analysis of the N-terminal amino acid sequence. The endonuclease gene was downstream from the methylase gene in the same orientation, separated by 69 bp. The promoter site, which could be recognized by Escherichia coli RNA polymerase, was upstream from the methylase gene, and the sequences adhering to the ribosome-binding sequence were identified in front of the respective genes. Analysis of the gene products expressed in E. coli cells by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the molecular weights of both enzymes coincided well with the values estimated from the nucleotide sequences, and that the monomeric forms were catalytically active. No significant similarity was found between the sequences of the two enzymes. Sequence comparison with other related enzymes indicated that FokI methylase contained two copies of a segment of tetra-amino acids which is characteristic of adenine-specific methylase.

Amino Acid Sequence↗
PubMedDate not supplied

[Modification of the modification-restriction system in staphylococci].

A new system of host specificity of DNA, called Sau67 according to the available nomenclature, was identified in Staphylococcus aureus 6782 strain by means of cross titration with staphylophage 729 considering that the phage exhibited the highly effective absorption properties. A total preparation of Sau67 methylases was isolated using ammonium sulfate fractionation. The enzyme preparation contained methylases of cytosine and adenine, where the activity of adenine methylases constituted only for 5% of the total methylase activity. As shown by kinetics of methylation low content of unspecific cellular nucleases was found in the St. aureus 6782 strain; these reasons are important for isolation of restricting endonucleases containing in the strain. 100 micrograms of protein of the total enzymatic fraction enabled to methylate the acceptory DNA at the maximal rate within 1.5 hr of incubation in phosphate buffer, pH 7.9. The fraction of cytosine methylases free of adenine methylating activity was obtained after chromatography on Sepharose blue with NaCl concentration stepwise gradient.

Chromatography, Agarose↗