Download MendeleyStructure of the branched intermediate in protein splicing.
Liu, Z., Frutos, S., Bick, M.J., Vila-Perello, M., Debelouchina, G.T., Darst, S.A., Muir, T.W.(2014) Proc Natl Acad Sci U S A 111: 8422-8427
- PubMed: 24778214
- DOI: https://doi.org/10.1073/pnas.1402942111
- Primary Citation of Related Structures:
4OZ6 - PubMed Abstract:
Inteins are autoprocessing domains that cut themselves out of host proteins in a traceless manner. This process, known as protein splicing, involves multiple chemical steps that must be coordinated to ensure fidelity in the process. The committed step in splicing involves attack of a conserved Asn side-chain amide on the adjacent backbone amide, leading to an intein-succinimide product and scission of that peptide bond. This cleavage reaction is stimulated by formation of a branched intermediate in the splicing process. The mechanism by which the Asn side-chain becomes activated as a nucleophile is not understood. Here we solve the crystal structure of an intein trapped in the branched intermediate step in protein splicing. Guided by this structure, we use protein-engineering approaches to show that intein-succinimide formation is critically dependent on a backbone-to-side-chain hydrogen-bond. We propose that this interaction serves to both position the side-chain amide for attack and to activate its nitrogen as a nucleophile. Collectively, these data provide an unprecedented view of an intein poised to carry out the rate-limiting step in protein splicing, shedding light on how a nominally nonnucleophilic group, a primary amide, can become activated in a protein active site.
Organizational Affiliation:
Frick Laboratory, Department of Chemistry, Princeton University, Princeton, NJ 08544; and.
