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Conservative replacement

  (Redirected from Conservative mutation)

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).[1][2]

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.[1]

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A multiple sequence alignment, produced by ClustalO, of five mammalian histone H1 proteins.
Sequences are the amino acids for residues 120-180 of the proteins. Residues that are conserved across all sequences are highlighted in grey. Below each site (i.e., position) of the protein sequence alignment is a key denoting conserved sites (*), sites with conservative replacements (:), sites with semi-conservative replacements (.), and sites with non-conservative replacements ( ).[3]

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.

Class Amino acids
Aliphatic Glycine, Alanine, Valine, Leucine, Isoleucine
Hydroxyl or sulfur/selenium-containing Serine, Cysteine, Selenocysteine, Threonine, Methionine
Cyclic Proline
Aromatic Phenylalanine, Tyrosine, Tryptophan
Basic Histidine, Lysine, Arginine
Acidic and their amides Aspartate, Glutamate, Asparagine, Glutamine

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