Protein

A protein (in Greek πρωτεϊνη = first thread) is a complex, high-molecular-weight organic compound that consists of amino acids joined by peptide bonds. Proteins are essential to the structure and function of all living cells and viruses.

Functions

Proteins are involved in practically every function performed by a cell, including regulation of cellular functions such as signal transduction and metabolism.

Related Topics:
Signal transduction - Metabolism

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For example, protein catabolism requires enzymes termed proteases and other enzymes such as glycosidases.

Related Topics:
Catabolism - Protease - Glycosidase

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Mechanisms of protein regulation

Various molecules and ions are able to bind to specific sites on proteins. These sites are called binding sites. They exhibit chemical specificity. The particle that binds is called a ligand. The strength of ligand-protein binding is a property of the binding site known as affinity.

Related Topics:
Binding site - Chemical specificity - Ligand - Affinity

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Since proteins are involved in practically every function performed by a cell, the mechanisms for controlling these functions therefore depend on controlling protein activity. Regulation can involve a protein's shape or concentration. Some forms of regulation include:

Related Topics:
Shape - Concentration

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• Allosteric modulation: When the binding of a ligand at one site on a protein affects the binding of ligand at another site.
• Covalent modulation: When the covalent modification of a protein affects the binding of a ligand or some other aspect of the protein's function.