Sandbox GGC7

Insulin is a hormone that is secreted by the pancreas in response to an increased level of glucose in the blood, usually after a meal. Insulin stimulates the muscles and adipose tissue to take up and store the excess glucose. Insulin is a dipeptide that contains a A and B chain. The A chain has an N-terminal helix linked to an anti-parallel C-terminal helix. The B chain has a central helical segment. The two chains are connected by 2 di-sulphide bonds that join the N- and C-terminal helices of the A chain to the central helix of the B chain ^[1] . When the concentration of glucose in the blood drops, insulin is no longer needed and an insulin-degrading enzyme is produced in order to reduce the amount of insulin in the body.

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Structure

The insulin-degrading enzyme (IDE) is a highly conserved protease that uses zinc (Zn2+) as a cofactor in breaking down insulin and amyloid beta-proteins ^[4]. The structure of IDE is a monomer with two N-terminal domains, which forms the catalytic site and two C-terminal domains that facilitates the substrate binding. The N-terminal domains are connected to the C-terminal domains via a 28-residue loop that forms a chamber that is shaped like a triangular prism.

Domain 1 houses the active site with two histidine's (his 108 and his 112), one glutamate (Glu 189) and the Zn2+ ion cofactor. Several residues of domains 1 & 4 create a polar area of the triangular cavity, while residues of domains 2 & 3 create a nonpolar region of the cavity.

In the open conformation, the insulin protein enters the enzyme opening causing a conformational change that allows the enzyme to fully recognize the protein and catalyzes protein degradation.

Function

Disease

Relevance

Structural highlights

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