Reference: Groll M, et al. (2006) Crystal Structures of Salinosporamide A (NPI-0052) and B (NPI-0047) in Complex with the 20S Proteasome Reveal Important Consequences of beta-Lactone Ring Opening and a Mechanism for Irreversible Binding. J Am Chem Soc 128(15):5136-5141

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Abstract

The crystal structures of the yeast 20S proteasome core particle (CP) in complex with Salinosporamides A (NPI-0052; 1) and B (4) were solved at <3 A resolution. Each ligand is covalently bound to Thr1O(gamma) via an ester linkage to the carbonyl derived from the beta-lactone ring of the inhibitor. In the case of 1, nucleophilic addition to the beta-lactone ring is followed by addition of C-3O to the chloroethyl group, giving rise to a cyclic ether. The crystal structures were compared to that of the omuralide/CP structure solved previously, and the collective data provide new insights into the mechanism of inhibition and irreversible binding of 1. Upon opening of the beta-lactone ring, C-3O assumes the position occupied by a water molecule in the unligated enzyme and hinders deacylation of the enzyme-ligand complex. Furthermore, the resulting protonation state of Thr1NH(2) deactivates the catalytic N-terminus.

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Journal Article
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Groll M, Huber R, Potts BC
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