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Typical amino acids and their alternatives usually have similar physicochemical properties. Leucine is an example of a typical amino acid. Idiosyncratic amino acids - there are few similar amino acids that they can mutate to through single nucleotide substitution. In this case most amino acid replacements will be disruptive for protein function.
A conservative replacement (also called a conservative mutation or a conservative substitution or a homologous replacement) is an amino acid replacement in a protein that changes a given amino acid to a different amino acid with similar biochemical properties (e.g. charge, hydrophobicity and size). [1] [2]
Missense mutations code for a different amino acid. A missense mutation changes a codon so that a different protein is created, a non-synonymous change. [4] Conservative mutations result in an amino acid change. However, the properties of the amino acid remain the same (e.g., hydrophobic, hydrophilic, etc.).
There are three amino acids encoded by six different codons: serine, leucine, and arginine. Only two amino acids are specified by a single codon each. One of these is the amino-acid methionine, specified by the codon AUG, which also specifies the start of translation; the other is tryptophan, specified by the codon UGG.
Substituting an amino acid with another from the same category is more likely to have a smaller impact on the structure and function of a protein than replacement with an amino acid from a different category. Consequently, acceptance of point mutations depends heavily on the amino acid being replaced in the mutation, and the replacement amino acid.
Saturation mutagenesis of a single position in a theoretical 10-residue protein. The wild type version of the protein is shown at the top, with M representing the first amino acid methionine, and * representing the termination of translation. All 19 mutants at position 5 are shown below.
Site saturation mutagenesis is a type of site-directed mutagenesis. This image shows the saturation mutagenesis of a single position in a theoretical 10-residue protein. The wild type version of the protein is shown at the top, with M representing the first amino acid methionine, and * representing the termination of translation.
Point substitution mutations of a codon, classified by their impact on protein sequence. A synonymous substitution (often called a silent substitution though they are not always silent) is the evolutionary substitution of one base for another in an exon of a gene coding for a protein, such that the produced amino acid sequence is not modified.