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B Suri

Publications and source records attributed to B Suri.

6 recordsLinked to original sources
PubMed1988

Type III DNA restriction and modification systems EcoP1 and EcoP15. Nucleotide sequence of the EcoP1 operon, the EcoP15 mod gene and some EcoP1 mod mutants.

This paper presents the nucleotide sequence of the mod-res operon of phage P1, which encodes the two structural genes for the EcoP1 type III restriction and modification system. We have also sequenced the mod gene of the allelic EcoP15 system. The mod gene product is responsible for binding the system-specific DNA recognition sequences in both restriction and modification; it also catalyses the modification reaction. A comparison of the two mod gene product sequences shows that they have conserved amino and carboxyl ends but have completely different sequences in the middle of the molecules. Two alleles of the EcoP1 mod gene that are defective in modification but not in restriction were also sequenced. The mutations in both alleles lie within the non-conserved regions.

Amino Acid Sequence↗
PubMed1985

EcoA: the first member of a new family of type I restriction modification systems. Gene organization and enzymatic activities.

The characterization of the EcoA restriction-modification enzymes from Escherichia coli 15T- is described. The reactions catalysed by these enzymes are very similar to those catalysed by the classical type I restriction and modification enzymes, a family of genetically related proteins. The detailed mechanisms, particularly for DNA modification, differ. The genetic and transcriptional organizations are also very similar to those of the classical systems, despite the fact that EcoA is not allelic to the others. We demonstrate that the expression of the EcoA genes is controlled following conjugative transfer to other strains in such a way that no lethality is observed, probably because the recipient chromosome is completely modified before restriction activity is expressed.

Adenosine Triphosphate↗
PubMed1984

The EcoA restriction and modification system of Escherichia coli 15T-: enzyme structure and DNA recognition sequence.

The EcoA restriction enzyme from Escherichia coli 15T- has been isolated. It proves to be an unusual enzyme, clearly related functionally to the classical type I restriction enzymes. The basic enzyme is a two subunit modification methylase. Another protein species can be purified which by itself has no enzymatic activities but which converts the modification methylase to an ATP and S-adenosylmethionine-dependent restriction endonuclease. The DNA recognition sequence of EcoA has an overall structure that is very similar to previously determined type I sequences. It is: 5'-GAGNNNNNNNGTCA-3' 3'-CTCNNNNNNNCAGT-5' where N can be any nucleotide. Modification methylates the adenosyl residue in the specific trinucleotide and the adenosyl residue in the lower strand of the specific tetranucleotide.

Base Sequence↗
PubMed1982

Structural homologies among type I restriction-modification systems.

Structural homologies among different restriction systems of Escherichia coli and several Salmonella species have been investigated by immunological methods using antibodies prepared against two subunits of the E. coli K12 restriction enzyme, and by DNA hybridization experiments using different fragments of the E. coli K12 hsd genes as probes. The results with both techniques show a strong homology between the E. coli K12 and B restriction-modification systems, weaker but nevertheless marked homology between E. coli K12 and the Salmonella systems SB, SP, and SQ and, surprisingly, no homology between the E. coli K12 and A systems.

Base Sequence↗