Back بنية البروتين Arabic Estructura de les proteínes AST Struktura proteina BS Proteinstruktur German Proteina strukturo Esperanto Estructura de las proteínas Spanish ساختار پروتئین Persian Proteiinin rakenne Finnish Structure des protéines French Estrutura das proteínas Galician
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Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers – specifically polypeptides – formed from sequences of amino acids, which are the monomers of the polymer. A single amino acid monomer may also be called a residue, which indicates a repeating unit of a polymer. Proteins form by amino acids undergoing condensation reactions, in which the amino acids lose one water molecule per reaction in order to attach to one another with a peptide bond. By convention, a chain under 30 amino acids is often identified as a peptide, rather than a protein.[1] To be able to perform their biological function, proteins fold into one or more specific spatial conformations driven by a number of non-covalent interactions, such as hydrogen bonding, ionic interactions, Van der Waals forces, and hydrophobic packing. To understand the functions of proteins at a molecular level, it is often necessary to determine their three-dimensional structure. This is the topic of the scientific field of structural biology, which employs techniques such as X-ray crystallography, NMR spectroscopy, cryo-electron microscopy (cryo-EM) and dual polarisation interferometry, to determine the structure of proteins.
Protein structures range in size from tens to several thousand amino acids.[2] By physical size, proteins are classified as nanoparticles, between 1–100 nm. Very large protein complexes can be formed from protein subunits. For example, many thousands of actin molecules assemble into a microfilament.
A protein usually undergoes reversible structural changes in performing its biological function. The alternative structures of the same protein are referred to as different conformations, and transitions between them are called conformational changes.
- ^ Stoker HS (1 January 2015). Organic and Biological Chemistry. Cengage Learning. p. 371. ISBN 978-1-305-68645-8.
- ^ Brocchieri L, Karlin S (10 June 2005). "Protein length in eukaryotic and prokaryotic proteomes". Nucleic Acids Research. 33 (10): 3390–3400. doi:10.1093/nar/gki615. PMC 1150220. PMID 15951512.