Mechanism of Action of Thalassospiramides, A New Class of Calpain Inhibitors

Liang Lu, Michael J. Meehan, Shuo Gu, Zhilong Chen, Weipeng Zhang, Gen Zhang, Lingli Liu, Xuhui Huang, Pieter C. Dorrestein, Ying Xu, Bradley S. Moore, Pei-Yuan Qian

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15 Scopus citations


Thalassospiramides comprise a large family of lipopeptide natural products produced by Thalassospira and Tistrella marine bacteria. Here we provide further evidence of their nanomolar inhibitory activity against the human calpain 1 protease. Analysis of structure-activity relationship data supported our hypothesis that the rigid 12-membered ring containing an α,β-unsaturated carbonyl moiety is the pharmacologically active functional group, in contrast to classic electrophilic "warheads" in known calpain inhibitors. Using a combination of chemical modifications, mass spectrometric techniques, site-directed mutagenesis, and molecular modeling, we show the covalent binding of thalassospiramide's α,β-unsaturated carbonyl moiety to the thiol group of calpain's catalytic Cys115 residue by a Michael 1,4-addition reaction. As nanomolar calpain inhibitors with promising selectivity and low toxicity from natural sources are rare, we consider thalassospiramides as promising drug leads.
Original languageEnglish (US)
JournalScientific Reports
Issue number1
StatePublished - Mar 5 2015
Externally publishedYes


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