Related Experiment Videos
Site-directed mutagenesis of Avibirnavirus VP4 gene
Juan Carlos Rodríguez-Lecompte1, Frederick S B Kibenge
1Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, Canada C1A 4P3.
Abstract:
Virus protein VP4 of infectious bursal disease virus (IBDV) is a protease which separates VPX and VP3 from the polyprotein. We studied the importance of serine and aspartic acid on cleavage at the VPX/VP4 junction and analysed the role of the proposed H547, D590, and S653 catalytic site using five different mutations on VP4. Our results suggest that the replacement of serine by lysine in AXAAS motifs in serotype II IBDV influences polyprotein (PP) processing by VP4 and also indicate the presence of an alternative cleavage site. Mutation on D ((510)TLAADK(515)) prevented the cleavage at the VPX/VP4 junction, but we have found that independently of the importance of those alanines in LAA, D has an important role as part of the cleavage site. Replacement of histidine by proline H547P completely abolished PP processing. Mutation on D590 induced a partial PP processing when it was replaced by proline and the replacement of serine by proline at S653P induced a prominent change in PP processing. These results permit us to conclude that IBDV VP4 has the ability to act according to structural and topographical changes during translational and posttranslational processes and allow multiple hit sites, which serve to increase effectiveness.
Insights
Infectious Bursal Disease Virus (IBDV) protein VP4 is a protease crucial for polyprotein processing. Mutations reveal key residues like aspartic acid and histidine are vital for VP4
Area of Science:
- Virology
- Molecular Biology
- Enzymology
Background:
- Infectious Bursal Disease Virus (IBDV) polyprotein processing is essential for viral replication.
- The viral protein VP4 acts as a protease, cleaving the polyprotein into functional subunits (VPX and VP3).
- Understanding the catalytic mechanisms of VP4 is key to deciphering viral maturation.
Purpose of the Study:
- To investigate the role of specific amino acid residues (serine, aspartic acid, histidine) in the catalytic activity of IBDV VP4.
- To analyze the function of the proposed catalytic triad (H547, D590, S653) in VP4-mediated polyprotein cleavage.
- To elucidate the impact of mutations on VP4's polyprotein processing efficiency and identify alternative cleavage sites.
Main Methods:
- Site-directed mutagenesis was employed to create five distinct mutations in the VP4 protein of IBDV.
- Polyprotein (PP) processing was analyzed following these mutations.
- The cleavage activity at the VPX/VP4 junction was specifically assessed.
Main Results:
- Mutation of aspartic acid at position 510 (D510) within the TLAADK motif completely inhibited cleavage at the VPX/VP4 junction, highlighting its critical role.
- Replacement of histidine at position 547 (H547P) abolished polyprotein processing, indicating its essentiality for VP4 function.
- Mutations at D590 and S653 resulted in partial or altered polyprotein processing, suggesting their involvement in the catalytic site and potentially alternative cleavage mechanisms.
- Alterations in the AXAAS motif (serine to lysine) in serotype II IBDV influenced polyprotein processing and suggested alternative cleavage sites.
Conclusions:
- IBDV VP4 protease activity is critically dependent on specific residues, including aspartic acid and histidine, within its catalytic site.
- The study confirms the importance of the H547, D590, and S653 residues for efficient polyprotein processing.
- IBDV VP4 exhibits adaptability to structural changes and possesses multiple cleavage sites, enhancing its functional effectiveness during viral replication.