Allosteric protein

Allosteric protein is a type of protein that changes its conformation, or shape, in response to a ligand binding to an allosteric (non-active) site, resulting in a functional change. This process is known as allosteric regulation, which plays a crucial role in many biological processes, including cell signaling, metabolism, and gene expression.

Overview

Allosteric proteins are found in a variety of biological systems and are essential for many cellular functions. They are often involved in the regulation of enzyme activity, ion channel gating, and signal transduction pathways. The term "allosteric" comes from the Greek words "allos" (other) and "stereos" (space), referring to the effect of the ligand binding at a site other than the active site.

Structure and Function

Allosteric proteins have multiple binding sites: the active site, where the substrate binds, and one or more allosteric sites, where the regulatory ligands bind. The binding of a ligand to the allosteric site induces a conformational change in the protein, which can either enhance or inhibit the protein's activity.

There are two main models of allosteric regulation: the concerted model and the sequential model. In the concerted model, proposed by Monod, Wyman, and Changeux, the protein switches between active and inactive states, and the binding of a ligand stabilizes the active state. In the sequential model, proposed by Koshland, Nemethy, and Filmer, the binding of a ligand induces a conformational change in a single subunit, which then affects the other subunits.

Examples

Examples of allosteric proteins include hemoglobin, which transports oxygen in the blood, and phosphofructokinase, a key enzyme in glycolysis. In both cases, the binding of a ligand to the allosteric site regulates the protein's activity.

See Also

• Cooperativity
• Enzyme kinetics
• Protein dynamics
• Protein structure