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Journal of Virology, February 2006, p. 1451-1462, Vol. 80, No. 3
0022-538X/06/$08.00+0 doi:10.1128/JVI.80.3.1451-1462.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, United Kingdom,1 Axon Neuroscience GmbH, Rennweg 95b, 1030 Vienna, Austria,2 Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, Institute of Medical Biochemistry, Medical University of Vienna, Dr. Bohr-Gasse 9/3, A-1030 Vienna, Austria3
Received 2 August 2005/ Accepted 15 November 2005
The 2A proteinases (2Apro) from the picornavirus family are multifunctional cysteine proteinases that perform essential roles during viral replication, involving viral polyprotein self-processing and shutting down host cell protein synthesis through cleavage of the eukaryotic initiation factor 4G (eIF4G) proteins. Coxsackievirus B4 (CVB4) 2Apro also cleaves heart muscle dystrophin, leading to cytoskeletal dysfunction and the symptoms of human acquired dilated cardiomyopathy. We have determined the solution structure of CVB4 2Apro (extending in an N-terminal direction to include the C-terminal eight residues of CVB4 VP1, which completes the VP1-2Apro substrate region). In terms of overall fold, it is similar to the crystal structure of the mature human rhinovirus serotype 2 (HRV2) 2Apro, but the relatively low level (40%) of sequence identity leads to a substantially different surface. We show that differences in the cI-to-eI2 loop between HRV2 and CVB4 2Apro translate to differences in the mechanism of eIF4GI recognition. Additionally, the nuclear magnetic resonance relaxation properties of CVB4 2Apro, particularly of residues G1 to S7, F64 to S67, and P107 to G111, reveal that the substrate region is exchanging in and out of a conformation in which it occupies the active site with association and dissociation rates in the range of 100 to 1,000 s1. This exchange influences the conformation of the active site and points to a mechanism for how self-processing can occur efficiently while product inhibition is avoided.
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