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Home > Quaternary structure


In biochemistry, many proteins are actually assemblies of more than one protein molecule, which in the context of the larger assemblage are known as protein subunits. In addition to the tertiary structure of the subunits, multiple-subunit proteins possess a quaternary structure, which is the arrangement into which the subunits assemble. Enzymes composed of subunits with diverse functions are sometimes called holoenzymes, in which some parts may be known as regulatory subunit s and the core is often called the catalytic subunit . Examples of proteins with quaternary structure include hemoglobin, DNA polymerase, and ion channels. Other assemblies referred to instead as multiprotein complexes also possess quaternary structure. Examples include nucleosomes and microtubules. Changes in quaternary structure are called conformational changes. It is through such changes, which underlie cooperativity and allostery in "multimeric" enzymes, that many proteins undergo regulation and perform their physiological function.

The above definition follows a classical approach to biochemistry, established at times when the disctinction between a protein and a functional, proteinaceous unit was difficult to elucidate. More recently, people refer to protein-protein interaction when discussing quaternary structure of proteins and consider all assemblies of proteins as protein complexes.

See also: primary structureprotein primary structure is a chain of amino acids. In biochemistry, to specify the primary structure of an unbranched biopolymer, such as a molecule of DNA, RNA or protein, is to name the species of every subunit ( nucleotide or amino acid) in order fro -- secondary structurealpha helices are shown in colour, and random coil in white, there are no beta sheets in shown. This protein was the first to have its structure solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, which led to them receivin -- tertiary structure -- structural biologyStructural biology is the study of the architecture and shape of biological macromolecules proteins and nucleic acids in particular--and what causes them to have the structures they have. This subject is of great interest to biologists, because macromolec -- translation

Protein structureProteins are amino acid chains, made up from 20 different L-α-amino acids, also referred to as residues, that fold into unique 3-dimensional protein structures . The shape into a which a protein naturally folds is known as its native state, which is

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