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A conservative replacement (also called a conservative mutation or a conservative substitution) is an amino acid replacement that changes a given amino acid to a different amino acid with similar biochemical properties (e.g. charge, hydrophobicity and size).
Conversely, a radical replacement, or radical substitution, is an amino acid replacement that exchanges an initial amino acid by a final amino acid with different physicochemical properties.
There are 20 naturally occurring amino acids, however some of these share similar characteristics. For example, leucine and isoleucine are both aliphatic, branched hydrophobes. Similarly, aspartic acid and glutamic acid are both small, negatively charged residues. Conservative replacements in proteins often have a smaller effect on function than non-conservative replacements. The reduced effect of conservative replacements on function can also be seen in the occurrence of different replacements in nature. Non-conservative replacements between proteins are far more likely to be removed by natural selection due to their deleterious effects.
Although there are many ways to classify amino acids, they are often sorted into six main groups on the basis of their structure and the general chemical characteristics of their R groups.
|Aliphatic||Glycine, Alanine, Valine, Leucine, Isoleucine|
|Hydroxyl or sulfur/selenium-containing||Serine, Cysteine, Selenocysteine, Threonine, Methionine|
|Aromatic||Phenylalanine, Tyrosine, Tryptophan|
|Basic||Histidine, Lysine, Arginine|
|Acidic and their amides||Aspartate, Glutamate, Asparagine, Glutamine|
- Zhang, Jianzhi (2000-01-01). "Rates of Conservative and Radical Nonsynonymous Nucleotide Substitutions in Mammalian Nuclear Genes". Journal of Molecular Evolution. 50 (1): 56–68. doi:10.1007/s002399910007. ISSN 0022-2844.
- Dagan, Tal; Talmor, Yael; Graur, Dan (2002-07-01). "Ratios of Radical to Conservative Amino Acid Replacement are Affected by Mutational and Compositional Factors and May Not Be Indicative of Positive Darwinian Selection". Molecular Biology and Evolution. 19 (7): 1022–1025. doi:10.1093/oxfordjournals.molbev.a004161. ISSN 0737-4038.
- "Clustal FAQ #Symbols". Clustal. Retrieved 8 December 2014.
- Graur, Dan (3 August 2015). "Radical and Conservative Amino-Acid Replacements". Judge Starling. Retrieved 2018-03-11.