Chemical specificity
Chemical specificity is the ability of a protein's binding site to bind specific ligands. The fewer ligands a protein can bind, the greater its specificity.
Specificity has its technical basis as an experimental measurement in enzyme kinetics, where the strength of binding between a given protein and ligand can be described by a dissociation constant, which characterizes the balance between bound and unbound states for the protein-ligand system. In the context of a single enzyme and a pair of binding molecules, the two ligands can be compared as stronger or weaker ligands (for the enzyme) on the basis of their dissociation constants. (A lower value corresponds to a stronger binding.)
Specificity for a set of ligands is unrelated to the ability of an enzyme to catalyze a given reaction, with the ligand as a substrate.
If a given enzyme has a high chemical specificity, this means that the set of ligands to which it binds is limited, such that neither binding events nor catalysis can occur at an appreciable rate with additional molecules.
An example of a protein-ligand pair whose binding activity can be described as highly specific is the antibody-antigen system. Conversely, an example of a protein-ligand system that can bind substrates and catalyze multiple reactions effectively is the Cytochrome P450 system, which can be considered a promiscuous enzyme due to its broad specificity for multiple ligands.
Applications of chemical specificity
Many scientific techniques, such as immunostaining, depend on chemical specificity. Immunostaining utilizes the chemical specificity of antibodies in order to detect a protein of interest at the cellular level [1]
References
- ↑ Maity, Biswanath; Sheff, David; Fisher, Rory A. (2013-01-01). "Immunostaining: detection of signaling protein location in tissues, cells and subcellular compartments". Methods in Cell Biology 113: 81–105. doi:10.1016/B978-0-12-407239-8.00005-7. ISSN 0091-679X. PMID 23317899.