4.1.4. Hsp40

Hsp40, also known as J protein, is mostly studied in its function as a co-chaperone with Hsp70. The Hsp40 family is divided into 3 types depending on the location of the J chain. In types I and II, the J-chain is located at the N-terminal, whereas in type-III, the J chain can be located anywhere in the protein sequence. The type-I protein additionally possesses two zinc finger motifs. The J chain, which is 70-amino-acid-residue long, stimulates the ATPase activity of Hsp70. Hsp40 is known to recognize and bind misfolded proteins and guide them to Hsp70 for folding. Hsp40 has been shown to play a crucial role in neurodegenerative diseases and cancers; however, its mechanism for recognizing non-proteins and modulating Hsp70 activity is poorly understood [77].
