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Crystal structure of coxsackievirus B3 3Dpol highlights the functional importance of residue 5 in picornavirus polymerases.

ABSTRACT: The crystal structure of the coxsackievirus B3 polymerase has been solved at 2.25-A resolution and is shown to be highly homologous to polymerases from poliovirus, rhinovirus, and foot-and-mouth disease viruses. Together, these structures highlight several conserved structural elements in picornaviral polymerases, including a proteolytic activation-dependent N-terminal structure that is essential for full activity. Interestingly, a comparison of all of the picornaviral polymerase structures shows an unusual conformation for residue 5, which is always located at a distortion in the beta-strand composed of residues 1 to 8. In our earlier structure of the poliovirus polymerase, we attributed this conformation to a crystal packing artifact, but the observation that this conformation is conserved among picornaviruses led us to examine the role of this residue in further detail. Here we use coxsackievirus polymerase to show that elongation activity correlates with the hydrophobicity of residue 5 and, surprisingly, more hydrophobic residues result in higher activity. Based on structural analysis, we propose that this residue becomes buried during the nucleotide repositioning step that occurs prior to phosphoryl transfer. We present a model in which the buried N terminus observed in all picornaviral polymerases is essential for stabilizing the structure during this conformational change.

SUBMITTER: Campagnola G

PROVIDER: S-EPMC2546958 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature

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Crystal structure of coxsackievirus B3 3Dpol highlights the functional importance of residue 5 in picornavirus polymerases.

Campagnola Grace G Weygandt Mark M Scoggin Kirsten K Peersen Olve O

Journal of virology 20080716 19

The crystal structure of the coxsackievirus B3 polymerase has been solved at 2.25-A resolution and is shown to be highly homologous to polymerases from poliovirus, rhinovirus, and foot-and-mouth disease viruses. Together, these structures highlight several conserved structural elements in picornaviral polymerases, including a proteolytic activation-dependent N-terminal structure that is essential for full activity. Interestingly, a comparison of all of the picornaviral polymerase structures show ...[more]

PMID: 18632862

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Project description:Coxsackievirus B3 (CVB3) is a common human pathogen that has been associated with serious diseases including myocarditis and pancreatitis. To better understand the effect of cytotoxic T-lymphocyte (CTL) responses in controlling CVB3 infection, we have inserted well-characterized CTL epitopes into the CVB3 genome. Constructs were made by placing the epitope of interest upstream of the open reading frame encoding the CVB3 polyprotein, separated by a poly-glycine linker and an artificial 3Cpro/3CDpro cleavage site. This strategy results in the foreign protein being translated at the amino- terminus of the viral polyprotein, from which it is cleaved prior to viral assembly. In this study, we cloned major histocompatibility complex class I-restricted CTL epitopes from lymphocytic choriomeningitis virus (LCMV) into recombinant CVB3 (rCVB3). In vitro, rCVB3 growth kinetics showed a 1- to 2-h lag period before exponential growth was initiated, and peak titers were approximately 1 log unit lower than for wild-type virus. rCVB3 replicated to high titers in vivo and caused severe pancreatitis but minimal myocarditis. Despite the high virus titers, rCVB3 infection of naive mice failed to induce a strong CD8+ T-cell response to the encoded epitope; this has implications for the proposed role of "cross-priming" during virus infection and for the utility of recombinant picornaviruses as vaccine vectors. In contrast, rCVB3 infection of LCMV-immune mice resulted in direct ex vivo cytotoxic activity against target cells coated with the epitope peptide, demonstrating that the rCVB3-encoded LCMV-specific epitope was expressed and presented in vivo. The preexisting CD8+ memory T cells could limit rCVB replication; compared to naive mice, infection of LCMV-immune mice with rCVB3 resulted in approximately 50-fold-lower virus titers in the heart and approximately 6-fold-lower virus titers in the pancreas. Although the inserted CTL epitope was retained by rCVB3 through several passages in tissue culture, it was lost in an organ-specific manner in vivo; a substantial proportion of viruses from the pancreas retained the insert, compared to only 0 to 1.8% of myocardial viruses. Together, these results show that expression of heterologous viral proteins by recombinant CVB3 provides a useful model for determining the mechanisms underlying the immune response to this viral pathogen.

Dataset Information

Crystal structure of coxsackievirus B3 3Dpol highlights the functional importance of residue 5 in picornavirus polymerases.

Publications

Crystal structure of coxsackievirus B3 3Dpol highlights the functional importance of residue 5 in picornavirus polymerases.

Similar Datasets

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