Resistance mutation
Encyclopedia
The term resistance mutation is most commonly used to describe point mutation
s in virus
gene
s that allow the virus to become resistant to treatment with a particular antiviral drug
. The term is now being seen with more frequency in bacteriology
and parasitology
. The term "resistance mutation" first appeared in the management of HIV
, which was the first virus in which genome sequencing is routinely used to look for drug resistance.
gene of HIV confers resistance to the drug lamivudine
. The letters stand for amino acid
s and use the traditional one letter abbreviations. M stands for methionine
, and V stands for valine
; 184 is the number of that amino acid position counting from the amino terminus of the protein. M184V means that the 184th amino acid of the protein is normally methionine, but that a mutation in the gene for that protein produces a form of the protein where that amino acid is substituted by valine instead.
The form V184 is sometimes seen; this means that the 184th amino acid of that protein is valine, but it gives no information as to whether that is a mutation or the normal state of affairs. The Greek capital letter delta Δ indicates a deletion: so ΔM184 would mean that the 184th amino acid is usually methionine, but that this position is now missing.
Alternatives are separated by slashes; so, M184V/I means "either M184V, or M184I".
Point mutation
A point mutation, or single base substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA. Often the term point mutation also includes insertions or deletions of a single base pair...
s in virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s that allow the virus to become resistant to treatment with a particular antiviral drug
Antiviral drug
Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses...
. The term is now being seen with more frequency in bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...
and parasitology
Parasitology
Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...
. The term "resistance mutation" first appeared in the management of HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
, which was the first virus in which genome sequencing is routinely used to look for drug resistance.
Nomenclature
Resistance mutations are conventionally listed as a letter, number and letter. For example, the M184V mutation in the reverse transcriptaseReverse transcriptase
In the fields of molecular biology and biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA. It also helps in the formation of a double helix DNA once the RNA has been reverse...
gene of HIV confers resistance to the drug lamivudine
Lamivudine
Lamivudine is a potent nucleoside analog reverse transcriptase inhibitor .It is marketed by GlaxoSmithKline with the brand names Zeffix, Heptovir, Epivir, and Epivir-HBV.Lamivudine has been used for treatment of chronic hepatitis B at a lower dose than for treatment of HIV...
. The letters stand for amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s and use the traditional one letter abbreviations. M stands for methionine
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
, and V stands for valine
Valine
Valine is an α-amino acid with the chemical formula HO2CCHCH2. L-Valine is one of 20 proteinogenic amino acids. Its codons are GUU, GUC, GUA, and GUG. This essential amino acid is classified as nonpolar...
; 184 is the number of that amino acid position counting from the amino terminus of the protein. M184V means that the 184th amino acid of the protein is normally methionine, but that a mutation in the gene for that protein produces a form of the protein where that amino acid is substituted by valine instead.
The form V184 is sometimes seen; this means that the 184th amino acid of that protein is valine, but it gives no information as to whether that is a mutation or the normal state of affairs. The Greek capital letter delta Δ indicates a deletion: so ΔM184 would mean that the 184th amino acid is usually methionine, but that this position is now missing.
Alternatives are separated by slashes; so, M184V/I means "either M184V, or M184I".