page_title: Hsp70
section_title: Structure
hierarchical_section_title: Hsp70 / Structure
caption_attribution_description: English: Hsp70 (pdb database 2KHO). Left domain is NBD (Nucleotide Binding domain) which can bind to ATP and ADP. Right lower domain is the groove, Subtrate Binding domain. Right upper domain is the "lip". (α-helices are shown in red. β-strands are shown in green.)
context_page_description: The 70 kilodalton heat shock proteins are a family of conserved ubiquitously expressed heat shock proteins. Proteins with similar structure exist in virtually all living organisms. The Hsp70s are an important part of the cell's machinery for protein folding, and help to protect cells from stress.
context_section_description: The Hsp70 proteins have three major functional domains:
  N-terminal ATPase domain – binds ATP (Adenosine triphosphate) and hydrolyzes it to ADP (Adenosine diphosphate). The NBD consists of two lobes with a deep cleft between them, at the bottom of which nucleotide (ATP and ADP) binds.  The exchange of ATP and ADP leads to conformational changes in the other two domains.
  Substrate binding domain – is composed of a 15 kDa β sheet subdomain and a 10 kDa helical subdomain. The β sheet subdomain consists of stranded β sheets with upward protruding loops, as a typical β barrel, which enclose the peptide backbone of the substrate. SBD contains a groove with an affinity for neutral, hydrophobic amino acid residues.  The groove is long enough to interact with peptides up to seven residues in length.
  C-terminal domain – rich in alpha helical structure acts as a 'lid' for the substrate binding domain.  The helical subdomain consists of five helices, with two helices packed against two sides of the β sheet subdomain, stabilizing the inner structure. In addition, one of the helix forms a salt bridge and several hydrogen bonds to the outer Loops, thereby closing the substrate-binding pocket like a lid. Three helices in this domain form another hydrophobic core which may be stabilization of the "lid". When an Hsp70 protein is ATP bound, the lid is open and peptides bind and release relatively rapidly.  When Hsp70 proteins are ADP bound, the lid is closed, and peptides are tightly bound to the substrate binding domain.
caption: Hsp70 (pdb database 2KHO). Left domain is NBD (Nucleotide Binding domain) which can bind to ATP and ADP. Right lower domain is the groove, Subtrate Binding domain. Right upper domain is the "lid". (α-helices are shown in red. β-strands are shown in green.)
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