Welcome! Click here to login or here to register.
Home
Proteins
DNA damage
Diseases
Homologs
Pathways
Keywords
Publications
Draw a picture
 
Search
 
Links
Help
Contact





Bujnicki Lab Homepage

DRR in Escherichia coli strain K-12 substr. MG1655

direct reversal repair

(also known as direct DNA damage reversal)

Proteins:
Ada
AlkB
Ogt
Phr


Cells are known to eliminate three types of damage to their DNA by chemically reversing it. These mechanisms do not require a template, since the types of damage they counteract can only occur in one of the four bases. Such direct reversal mechanisms are specific to the type of damage incurred and do not involve breakage of the phosphodiester backbone. The formation of pyrimidine dimers upon irradiation with UV light results in an abnormal covalent bond between adjacent pyrimidine bases. The photoreactivation process directly reverses this damage by the action of the enzyme photolyase CDP, whose activation is obligately dependent on energy absorbed from blue/UV light (300–500 nm wavelength) to promote catalysis. Another type of damage, methylation of guanine bases, is directly reversed by the protein methyl guanine methyl transferases Ogt and Ada. A generalized response to methylating agents in bacteria is known as the adaptive response and confers a level of resistance to alkylating agents upon sustained exposure by upregulation of alkylation repair enzymes. The third type of DNA damage reversed by cells is certain methylation of the bases cytosine and adenine by AlkB. AlkB specifically removes alkylation damage to single stranded (SS) DNA caused by SN2 type of chemical agents. It efficiently removes methyl groups from 1-methyl adenines, 3-methyl cytosines in SS DNA. Demethylation by AlkB is accompanied with release of CO2, succinate and formaldehyde.

Keywords:

alt alt alt alt
Add your own comment!

There is no comment yet.
Welcome stranger! Click here to login or here to register.
Valid HTML 4.01! This site is Emacs powered. Made with Django.