Escherichia coli/Methylation: Difference between revisions
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(New page: *Type I methylation systems: ** ''E. coli'' K-12 restricts DNA which is '''not''' protected by adenine methylation at sites AA<sup>*</sup>C[N<sub>6</sub>]GTGC or GCA<sup>*</sup>C[N<sub>6<...) |
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*Type I methylation systems: | *Type I methylation systems: | ||
** ''E. coli'' | ** ''E. coli'' K12 restricts DNA which is '''not''' protected by adenine methylation at sites AA<sup>*</sup>C[N<sub>6</sub>]GTGC or GCA<sup>*</sup>C[N<sub>6</sub>]GTT, encoded by the hsdRMS genes(EcoKI). Deletions in these genes removes either the restriction or methylation or both of these functions. | ||
** ''E. coli'' B derivative strains contain an hsdRMS system (EcoBI) restricting and | ** ''E. coli'' B derivative strains contain an hsdRMS system (EcoBI) restricting and protecting the sequence TGA<sup>*</sup>[N<sub>8</sub>]TGCT or AGCA<sup>*</sup>[N<sub>8</sub>]TCA. | ||
* The '''mcrA''' gene (carried on the e14 prophage) restricts DNA which '''is''' methylated in C<sup>m</sup>CWGG or <sup>m</sup>CG sequences (methylation by the '''dcm''' gene product). | * The '''mcrA''' gene (carried on the e14 prophage) restricts DNA which '''is''' methylated in C<sup>m</sup>CWGG or <sup>m</sup>CG sequences (methylation by the '''dcm''' gene product). | ||
* The '''mcrBC''' genes restrict R<sup>m</sup>C sequences. | * The '''mcrBC''' genes restrict R<sup>m</sup>C sequences. | ||
* The '''mrr''' gene product restricts adenine methylated sequences at CAG or GAC sites. | * The '''mrr''' gene product restricts adenine methylated sequences at CAG or GAC sites. | ||
* E. coli methylates the adenine in GATC (and the corresponding A on the opposite strand) with the '''dam''' gene product. | * E. coli methylates the adenine in GATC (and the corresponding A on the opposite strand) with the '''dam''' gene product. | ||
* M.EcoKII methylates the first A at the palindromic site ATGCAT (as well as the corresponding A on the opposite strand), see (Kossykh VG (2004) J. Bact 186: 2061-2067 PMID 15028690) Note that this article has been retracted; the retraction appears to center on textual plagarism, not experimental results. The homology to AvaIII is real. I think I believe it. [[User:Tk|tk]] 20:28, 9 December 2005 (EST). Rich Roberts reports: "We have tried ourselves to detect activity with this gene product and cannot detect any methyltransferase activity. In our case we used antibodies able to detect N6-methyladenine or N4 methylcytosine in DNA. The ones we have are very sensitive and should have been able to detect 5 methyl groups in the whole E. coli chromosome. Nothing was detected in an over expressing strain." | * M.EcoKII methylates the first A at the palindromic site ATGCAT (as well as the corresponding A on the opposite strand), see (Kossykh VG (2004) J. Bact 186: 2061-2067 PMID 15028690) Note that this article has been retracted; the retraction appears to center on textual plagarism, not experimental results. The homology to AvaIII is real. I think I believe it. [[User:Tk|tk]] 20:28, 9 December 2005 (EST). Rich Roberts reports: "We have tried ourselves to detect activity with this gene product and cannot detect any methyltransferase activity. In our case we used antibodies able to detect N6-methyladenine or N4 methylcytosine in DNA. The ones we have are very sensitive and should have been able to detect <font color=purple>5-methyl</font> groups in the whole E. coli chromosome. Nothing was detected in an over-expressing strain." | ||
*For additional information see [[E. coli restriction-modification system]] and the [http://www.neb.com/nebecomm/tech_reference/restriction_enzymes/making_unmethylated_dna.asp NEB technical information on methylation]. | *For additional information see [[E. coli restriction-modification system]] and the [http://www.neb.com/nebecomm/tech_reference/restriction_enzymes/making_unmethylated_dna.asp NEB technical information on methylation]. | ||
[[Category:Escherichia coli]] | [[Category:Escherichia coli]] | ||
Latest revision as of 18:52, 4 April 2013
- Type I methylation systems:
- E. coli K12 restricts DNA which is not protected by adenine methylation at sites AA*C[N6]GTGC or GCA*C[N6]GTT, encoded by the hsdRMS genes(EcoKI). Deletions in these genes removes either the restriction or methylation or both of these functions.
- E. coli B derivative strains contain an hsdRMS system (EcoBI) restricting and protecting the sequence TGA*[N8]TGCT or AGCA*[N8]TCA.
- The mcrA gene (carried on the e14 prophage) restricts DNA which is methylated in CmCWGG or mCG sequences (methylation by the dcm gene product).
- The mcrBC genes restrict RmC sequences.
- The mrr gene product restricts adenine methylated sequences at CAG or GAC sites.
- E. coli methylates the adenine in GATC (and the corresponding A on the opposite strand) with the dam gene product.
- M.EcoKII methylates the first A at the palindromic site ATGCAT (as well as the corresponding A on the opposite strand), see (Kossykh VG (2004) J. Bact 186: 2061-2067 PMID 15028690) Note that this article has been retracted; the retraction appears to center on textual plagarism, not experimental results. The homology to AvaIII is real. I think I believe it. tk 20:28, 9 December 2005 (EST). Rich Roberts reports: "We have tried ourselves to detect activity with this gene product and cannot detect any methyltransferase activity. In our case we used antibodies able to detect N6-methyladenine or N4 methylcytosine in DNA. The ones we have are very sensitive and should have been able to detect 5-methyl groups in the whole E. coli chromosome. Nothing was detected in an over-expressing strain."
- For additional information see E. coli restriction-modification system and the NEB technical information on methylation.
