hjálparpróteinum

Hjálparpróteinum, or chaperone proteins, are a diverse group of proteins that assist other proteins in achieving and maintaining their proper three-dimensional structure. They do not form part of the final structure of client proteins but guide their folding, assembly, and stabilization, and can prevent aggregation during synthesis and stress.

Chaperones operate through cycles of substrate binding and release, often powered by ATP hydrolysis. Major families include Hsp70s, Hsp90s, and chaperonins such as the Hsp60 family (bacterial GroEL/GroES and their equivalents in mitochondria and chloroplasts) and eukaryotic CCT/TriC complexes. Small heat shock proteins stabilize unfolded polypeptides, while co-chaperones and nucleotide exchange factors regulate substrate binding and release.

When a protein cannot fold correctly, chaperones may help refold it or direct it toward degradation pathways, contributing to cellular proteostasis. In response to heat or other stresses, cells upregulate chaperones, a response coordinated by heat shock transcription factors.

Chaperones participate in protein targeting and assembly of multiprotein complexes, assist in mitochondrial import, and can be involved in autophagy, including chaperone-mediated autophagy. Malfunction or imbalance of chaperones is linked to diseases involving protein misfolding and aggregation, though their activity is essential for development and normal physiology.