Hsp70: Difference between revisions

The uncovering structure of the various proteins in the Hsp70 family is still underway, but for the most part the general structure is known. The 70 in its name refers to its molecular mass. All members of the Hsp70 family have an N-terminal nucleotide binding domain (NBD)(~40 kDa) and a C-terminal <scene name='81/813405/Scene_alex_2/1'>substrate-binding domain (SBD)</scene> (~25 kDa) connected by a short linker. The NBD consists of two subdomains, I and II, which are further divided into regions a and b. The Ia and IIa subdomains interact with ATP through a nucleotide-binding cassette <scene name='81/813405/Alex_scene_1/3'>[ATPase Domain]</scene> related to those of hexokinase, actin and glycerol kinase. A Ramachandran plot can be viewed <scene name='81/813405/Scene_alex_5/2'>here</scene>. The SBD consists of a 10-kD α-helix subdomain and a 15-kDa β-sandwich. Crystal structures suggest that substrate peptides are bound in an extended conformation between loops of the β-sandwich and that the α-helix subdomain acts as a “lid.”  The Ramachandran plot can be viewed here. Numerous functions of this protein rely on the communication between the ATPase domain activity within the NBD and the SBD <ref name="Evans"/>. This makes sense because the energy rendered from ATP hydrolysis in the ATPase Domain can be used by the substrate binding domain to perform its function. This is allosterically controlled by ATP binding.