Deamination of cytosine
Cytosine susceptible to hydrolysis deaminated to uracil. If left uncorrected, the conversion of cytosine to uracil mutations migration occurs. It is a base for foreign DNA, uracil, will change back enzyme specific cytosine, uracil DNA glycosylase to (UDG).
Deamidation is by removing the amino groups of the molecule. Enzyme that catalyzes this reaction, known as deaminase. The human body, deamination takes place mainly in the liver, but glutamic acid, is deaminated in the kidney. If there is an excess of proteins, is a process when the deamidation amino acid is split. It is removed from an amino acid, an amino group is converted to ammonia. Consists essentially of carbon and hydrogen, the rest of the amino acid sequence is oxidized or recycled as energy. Ammonia is toxic to the human body, the enzyme converts the uric acid and urea by adding a molecule (which is not considered in the deamidation process) carbon dioxide in the urea cycle, which takes place in the liver. Uric acid and urea, can be safely after diffused in the blood and excreted in the urine.
Release of ammonia in the process, deamination spontaneous reaction is a hydrolysis of cytosine to uracil. Instead of the bisulfite to convert cytosine, 5 – and can be prepared by in vitro of using the methylcytosine. This property has been allowed for researchers to distinguish between methylated cytosine (shown as uracil) unmethylated cytosine to sequence methylated DNA. The DNA, the deamination spontaneous is adjusted removal of uracil uracil DNA glycosylase generator of abasic (AP) site (rather than cytosine deamination, the product of the portion of the DNA) by. By replacing cytosine another abasic sites obtained is recognized by the (AP endonuclease) enzymes that degrade to allow repair of the lesion, the phosphodiester bonds of DNA. DNA polymerase is able to fill the reaction of the polymerase activity by nick translation terminal excision reaction due to the 3′-> 5 ‘exonuclease activity, to perform this substitution followed. DNA ligase to form a phosphodiester bond sealing the two strand nicks resulting product contains a new, correct cytosine.
5 – methylcytosine is a methylated form of the DNA base cytosine, which can be incorporated in the regulation of gene transcription. Cytosine is methylated, DNA sequences, to maintain the same, but (which is part of the field of genetics for this study) methyl gene expression may vary. 5 – methylcytosine, nucleoside, 5 – incorporated into methylcytidine. (As opposed to the 6 o’clock position nitrogen NH, clockwise counted from 02 h) is attached to the 5-position of the atoms in the six ring atoms methylcytosine, a methyl group – 5. Distinguish methyl cytosine – this methyl group, 5.
When trying to separate the bacterial toxins responsible for tuberculosis, separating the nucleic acids called tuberculinic acid in 1898 by a new M. tuberculosis WG Ruppel. The nucleic acid, in addition methylated nucleotides, guanine, cytosine and thymine, can be included in it unusual was found. 1925, to detect the minor methylated cytosine derivative as a hydrolysis product of tuberculinic acid and sulfuric acid Coghill normal and Johnson. This report was criticized for the identification of those based on the optical properties of crystalline picric acid exclusively rapidly, other scientists did not have the ability to reproduce the same results. Using a paper chromatography to establish a methylated cytosine unique completely different uracil and cytosine conventional, when it is divided into the nucleic acid of calf thymus DNA, and finally, stapler, facts 1948 But I was found. After 70 years, the precise role is unclear, but also, it should be a common feature of the RNA molecule in a variety was found.
Life, seems to be designed to minimize the error. The universal nature of proof-reading/repair machine, to optimize the genetic code, parity sign of the G / C :/ T will all agree on this point. However, in spite of the logic of this design, cytosine, is particularly sensitive to deamination, such as removal of the exocyclic amino group is interesting, but there, it will be a (base, which is normally found in RNA) uracil. Uracil in DNA is not present, it can be removed by detecting the repair enzymes it effectively. If it is detected, it is not deleted, base pair with adenine, which means that you specify the adenine during DNA replication can be it. I set the thymine in subsequent rounds of replication of adenine in order. The conclusion is that the deamination spontaneous cytosine, there is a possibility that base substitutions called transition is replaced by (being substituted with the other strand of the DNA and G) T is C occurs. I can expect that the conversion to C half-life single-stranded DNA of cytosine for specific about 200 years certain cytosine deamination degree, since such mutations are a common occurrence at 37. In fact, the high rate of these deamidation, led researchers from the pool. Al complain of “confusion cytosine”