chaperones

Chaperones are a diverse group of proteins that assist other proteins in achieving and maintaining their proper three-dimensional structure. They are not permanently part of the proteins they help; instead, they act transiently to guide folding, prevent misfolding and aggregation, assist in assembly of multi-subunit complexes, and sometimes facilitate transport across membranes or targeting to degradation. Chaperones are especially important under cellular stress, where misfolded proteins accumulate.

Molecular chaperones include several families. Hsp70s (including the bacterial DnaK) work with co-chaperones such as Hsp40/DnaJ and GrpE to bind and release substrates in an ATP-dependent cycle. Hsp60 chaperonins (GroEL/GroES in bacteria; their equivalents in organelles) provide an isolated folding chamber. Hsp90 assists maturation of signaling proteins and some receptors, often with a range of co-chaperones. Small heat shock proteins (sHSPs) act as holdases, binding unfolded polypeptides to prevent aggregation. A broader class, the chaperonin/chaperone machinery, often uses ATP hydrolysis to drive conformational changes and substrate release.

Biological significance and applications: Proper chaperone function is essential for proteome stability; failures are linked to neurodegenerative diseases and aging. In biotechnology and biomedicine, chaperones are exploited to improve folding of recombinant proteins or to modulate protein quality control. In cancer research, inhibitors of Hsp90 have been explored as anticancer therapies due to their role in stabilizing many oncoproteins.

In a social context, the term chaperone also refers to a person who accompanies others to events or outings, providing supervision, safety, or guidance. The term is often used for chaperoning students on field trips or younger travelers, though its usage varies by region.