Related Experiment Video
Updated: Jun 12, 2026
10:40
Analysis of Group IV Viral SSHHPS Using In Vitro and In Silico Methods
Published on: December 21, 2019
Structural basis for substrate specificity of alphavirus nsP2 proteases
Andrew T Russo1, Robert D Malmstrom, Mark A White
1Department of Biochemistry and Molecular Biology and the Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555-0647, USA.
Journal of Molecular Graphics & Modelling
|May 21, 2010
Summary
Alphavirus nsP2 protease activity is key for viral replication. Molecular dynamics and structural studies reveal how this protease recognizes specific viral polyprotein cleavage sites, explaining its specificity across strains.
Area of Science:
- Virology
- Structural Biology
- Biochemistry
Background:
- The alphavirus nsP2 protease is crucial for processing the nonstructural polyprotein (nsP1234) and enabling viral genome replication.
- Understanding the nsP2 protease's catalytic mechanism and substrate specificity is vital for alphavirus research.
Purpose of the Study:
- To elucidate the structural and molecular features governing the substrate specificity of the alphavirus nsP2 protease.
- To investigate the catalytic mechanism and identify key residues involved in cleavage site recognition.
Main Methods:
- Combined molecular dynamics (MD) simulations with structural studies.
- Analyzed bimolecular complexes of Venezuelan equine encephalitis virus (VEEV) nsP2 protease with cleavage sites.
- Employed homology modeling to study diverse alphaviruses.
Main Results:
- The nsP2 protease mechanism resembles papain-like cysteine proteases, involving a catalytic dyad forming a thiolate-imidazolium ion pair.
- Identified specific protease residues (His510, Ser511, His546, Lys706) critical for Venezuelan equine encephalitis virus nsP2 protease cleavage site recognition.
- Revealed conserved and strain-specific substrate recognition features across alphaviruses, including compensatory mutations in binding site residues.
Conclusions:
- The study explains how alphavirus nsP2 proteases recognize diverse cleavage sites within the nonstructural polyprotein.
- Identified mechanisms of discrimination between closely related cleavage targets, offering insights into alphavirus evolution and control.
Related Concept Videos
02:28Leaky Scanning
During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA. Marilyn Kozak discovered that the sequence RCCAUGG (where R stands for...
01:19Allosteric Proteins-ATCase
Binding sites linkages can regulate a protein's function. For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
02:27Predicting Products: SN1 vs. SN2
Nucleophilic substitution reactions of alkyl halides can proceed via an SN1 or an SN2 mechanism. While in SN2 reactions, the nucleophile attacks the substrate simultaneously as the leaving group departs, in SN1 reactions, the substrate first dissociates to give the carbocation intermediate. Various factors such as the structure of the substrate, the strength of the nucleophile, and the nature of the solvent promote one mechanism over the other.
With increased substitution on the alkyl halide,...
With increased substitution on the alkyl halide,...
02:27SN2 Reaction: Mechanism
The kinetic studies of SN2 reactions suggest an essential feature of its mechanism: it is a single-step process without intermediates. Here, both the nucleophile and the substrate participate in the rate-determining step.
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
01:25Inhibitors Of Virion Release
Viral replication and dissemination rely on efficient mechanisms for host cell entry, genome replication, assembly, and release. Influenza viruses, such as types A and B, are negative-sense single-stranded RNA viruses with a segmented genome, that depend on two critical surface glycoproteins to carry out these processes: hemagglutinin (HA) and neuraminidase (NA). HA initiates infection by binding to sialic acid residues on the surface of host epithelial cells, facilitating receptor-mediated...
02:26SN2 Reaction: Transition State
An SN2 reaction of an alkyl halide is a single-step process in which bond formation between the nucleophile and the substrate and bond breaking between the substrate and the halide occurs simultaneously through a transition state without forming an intermediate.
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...