How can a missense mutation change a protein’s function?

A missense mutation is a type of point mutation where a change in a single DNA base pair results in the substitution of one amino acid for another in the final protein sequence.12

Because proteins rely on a specific amino acid composition and sequence to maintain their structure and function, replacing an amino acid with one that is functionally different can disrupt the protein's activity. This process can lead to the alteration or complete loss of protein function.132

For example, enzymes are particularly vulnerable to these mutations if the substitution occurs at their active site—the specific region where the enzyme binds to its substrate. If the amino acid change prevents this binding, the enzyme may become inactive, even if the rest of the protein is synthesized correctly. While some mutations are "leaky," allowing some normal function to persist, others result in a "null" mutation where the protein loses its biological utility entirely.2