Proteiinifoldingin

Proteiinifoldingin is the process by which a linear chain of amino acids folds into a specific three-dimensional structure that enables biological function. It is commonly referred to as protein folding in most scientific literature. The folding outcome is determined mainly by the amino acid sequence; the native structure is often the global minimum of free energy under physiological conditions. Folding involves forming local secondary structures, hydrophobic collapse, and the packing of side chains, guided by hydrogen bonds, ionic interactions, van der Waals forces, and sometimes disulfide bonds. The process is influenced by the cellular environment and can be described by energy landscapes and folding funnels, which explain how fast folders reach their native state despite many possible conformations.

Molecular chaperones and folding machines assist in challenging cases. In bacteria, chaperonins GroEL/GroES help proteins fold in isolation; in eukaryotes, other chaperones such as Hsp70, Hsp90, and the TRiC/CCT complex play roles; the endoplasmic reticulum provides quality control for secreted and membrane proteins. Misfolding and aggregation are harmful; misfolded proteins can aggregate into amyloid fibrils, associated with diseases such as Alzheimer's, Parkinson's, prion diseases, and cystic fibrosis.

Techniques to study folding include spectroscopic methods, X-ray crystallography, NMR, and cryo-EM; computational methods include molecular dynamics and structure prediction with AlphaFold or Rosetta. History: Anfinsen's experiments showed that a protein's amino acid sequence determines its structure; the Levinthal paradox and the development of energy landscape theory shaped the field. Impact: understanding folding informs drug design, protein engineering, and disease research.