BAG domain

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PDB 1hx1 EBI.jpg
crystal structure of a bag domain in complex with the hsc70 atpase domain
Symbol BAG
Pfam PF02179
InterPro IPR003103
SCOP 1hx1

In molecular biology, BAG domains are protein domains found in proteins which are modulators of chaperone activity, they bind to HSP70/HSC70 proteins and promote substrate release. The proteins have anti-apoptotic activity and increase the anti-cell death function of BCL-2 induced by various stimuli. BAG-1 binds to the serine/threonine kinase Raf-1 or Hsc70/Hsp70 in a mutually exclusive interaction. BAG-1 promotes cell growth by binding to and stimulating Raf-1 activity. The binding of Hsp70 to BAG-1 diminishes Raf-1 signalling and inhibits subsequent events, such as DNA synthesis, as well as arrests the cell cycle. BAG-1 has been suggested to function as a molecular switch that encourages cells to proliferate in normal conditions but become quiescent under a stressful environment .[1]

BAG-family proteins contain a single BAG domain, except for human BAG-5 which has four BAG repeats. The BAG domain is a conserved region located at the C terminus of the BAG-family proteins that binds the ATPase domain of Hsc70/Hsp70. The BAG domain is evolutionarily conserved, and BAG domain containing proteins have been described and/or proven in a variety of organisms including Mus musculus (Mouse), Xenopus spp., Drosophila spp., Bombyx mori (Silk moth), Caenorhabditis elegans, Saccharomyces cerevisiae (Baker's yeast), Schizosaccharomyces pombe (Fission yeast), and Arabidopsis thaliana (Mouse-ear cress).

The BAG domain has 110-124 amino acids and is composed of three anti-parallel alpha-helices, each approximately 30-40 amino acids in length. The first and second helices interact with the serine/threonine kinase Raf-1 and the second and third helices are the sites of the BAG domain interaction with the ATPase domain of Hsc70/Hsp70. Binding of the BAG domain to the ATPase domain is mediated by both electrostatic and hydrophobic interactions in BAG-1 and is energy requiring.


  1. ^ Doong H, Vrailas A, Kohn EC (December 2002). "What's in the 'BAG'?--A functional domain analysis of the BAG-family proteins". Cancer Lett. 188 (1-2): 25–32. doi:10.1016/S0304-3835(02)00456-1. PMID 12406544. 

This article incorporates text from the public domain Pfam and InterPro IPR003103