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Ogt
Encyclopedia
O6-alkyl guanine transferase II (O6 AGT II) previously known as O6 Guanine transferase (ogt) is a protein that is involved in DNA repair
with Ada
.
Like Ada, AGT II is responsible for the removal of alkyl groups from O6-alkyl guanine
, O4-alkyl thymine
and alkyl phosphotriester in the sugar-phosphate backbone of DNA. AGT II shows a greater preference for O4-alkyl thymine than O6-alkyl guanine and alkyl phosphotriester.
Unlike Ada, AGT II is expressed constitutively in cells. Therefore, AGT II will repair alkylated DNA adduct
s even before Ada is fully induced. AGT II is similar to Ada in its suicide inactivation
in that AGT II transfers the alkyl group to a cysteine residue in its own structure, thereby inactivating itself. The human equivalent of AGT II is MGMT (O6-methyl guanine methyl transferase). MGMT preferentially removes alkyl groups from O6-alkyl guanine than from O4–alkyl thymine.
DNA repair
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1...
with Ada
Ada (protein)
Ada is an enzyme induced by treatment of bacterial cells with alkylating agents that mainly cause methylation damage. This phenomenon is called the adaptive response and hence the name. Ada is also called as O6 alkyl guanine transferase I . Ada transfers the alkyl group from DNA bases and...
.
Like Ada, AGT II is responsible for the removal of alkyl groups from O6-alkyl guanine
Guanine
Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...
, O4-alkyl thymine
Thymine
Thymine is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. As the name suggests, thymine may be derived by methylation of uracil at...
and alkyl phosphotriester in the sugar-phosphate backbone of DNA. AGT II shows a greater preference for O4-alkyl thymine than O6-alkyl guanine and alkyl phosphotriester.
Unlike Ada, AGT II is expressed constitutively in cells. Therefore, AGT II will repair alkylated DNA adduct
DNA adduct
In molecular genetics, a DNA adduct is a piece of DNA covalently bonded to a chemical. This process could be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as biomarkers of exposure and as such are themselves measured to reflect quantitatively,...
s even before Ada is fully induced. AGT II is similar to Ada in its suicide inactivation
Suicide inhibition
Suicide inhibition, also known as suicide inactivation or mechanism-based inhibition, is a form of irreversible enzyme inhibition that occurs when an enzyme binds a substrate analogue and forms an irreversible complex with it through a covalent bond during the "normal" catalysis reaction...
in that AGT II transfers the alkyl group to a cysteine residue in its own structure, thereby inactivating itself. The human equivalent of AGT II is MGMT (O6-methyl guanine methyl transferase). MGMT preferentially removes alkyl groups from O6-alkyl guanine than from O4–alkyl thymine.