Serpin

The native state of serpins is an equilibrium between a fully stressed state (left) and a partially relaxed state (right). The five-stranded A-sheet (light blue) contains two functionally important regions for the serpin's mechanism, the breach and the shutter. The reactive centre loop (RCL, blue) exists in a dynamic equilibrium between the fully exposed conformation (left) and a conformation where it is partially inserted into the breach of the A-sheet (right).(PDB: 1QLP, 1YXA)[42][43]

The inhibitory mechanism of serpins involves a large conformational change (S to R transition). The serpin (white) first binds a protease (grey) with the exposed reactive centre loop (blue). When this loop is cleaved by the protease, it rapidly inserts into the A-sheet (light blue), deforming and inhibiting the protease. (PDB: 1K9O, 1EZX)Serine and cysteine proteases operate by a two-step catalytic mechanism. First, the substrate (blue) is attacked by the cysteine or serine of the catalytic triad (red) to form an acyl-enzyme intermediate. For typical substrates, the intermediate is resolved by hydrolysis by water. However, when the reactive centre loop (RCL) of a serpin is attacked, the conformational change (blue arrow) pulls the catalytic triad out of position, preventing it from completing catalysis. (Based on PDB: 1K9O, 1EZX)

Serpins are a superfamily of proteins with similar structures that were first identified for their protease inhibition activity and are found in all kingdoms of life. The acronym serpin was originally coined because the first serpins to be identified act on chymotrypsin-like serine proteases (serine protease inhibitors). They are notable for their unusual mechanism of action, in which they irreversibly inhibit their target protease by undergoing a large conformational change to disrupt its active site. This contrasts with the more common competitive mechanism for protease inhibitors that bind to and block access to the protease active site.

单词	Serpin superfamily
释义	Serpin superfamily 英语百科 Serpin Serpins are a superfamily of proteins with similar structures that were first identified for their protease inhibition activity and are found in all kingdoms of life. The acronym serpin was originally coined because the first serpins to be identified act on chymotrypsin-like serine proteases (serine protease inhibitors). They are notable for their unusual mechanism of action, in which they irreversibly inhibit their target protease by undergoing a large conformational change to disrupt its active site. This contrasts with the more common competitive mechanism for protease inhibitors that bind to and block access to the protease active site.
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Serpin superfamily

Serpin