Harrop SJ, Jankova L, Coles M, Jardine D, Whittaker JS, Gould AR, Meister A, King GC, Mabbutt BC, Curmi PM. The crystal structure of plasminogen activator inhibitor 2 at 2.0 A resolution: implications for serpin function.
Structure 1999;
7:43-54. [PMID:
10368272 DOI:
10.1016/s0969-2126(99)80008-2]
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Abstract
BACKGROUND
Plasminogen activator inhibitor 2 (PAI-2) is a member of the serpin family of protease inhibitors that function via a dramatic structural change from a native, stressed state to a relaxed form. This transition is mediated by a segment of the serpin termed the reactive centre loop (RCL); the RCL is cleaved on interaction with the protease and becomes inserted into betasheet A of the serpin. Major questions remain as to what factors facilitate this transition and how they relate to protease inhibition.
RESULTS
The crystal structure of a mutant form of human PAI-2 in the stressed state has been determined at 2.0 A resolution. The RCL is completely disordered in the structure. An examination of polar residues that are highly conserved across all serpins identifies functionally important regions. A buried polar cluster beneath betasheet A (the so-called 'shutter' region) is found to stabilise both the stressed and relaxed forms via a rearrangement of hydrogen bonds.
CONCLUSIONS
A statistical analysis of interstrand interactions indicated that the shutter region can be used to discriminate between inhibitory and non-inhibitory serpins. This analysis implied that insertion of the RCL into betasheet A up to residue P8 is important for protease inhibition and hence the structure of the complex formed between the serpin and the target protease.
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