Foot-and-mouth disease (FMD) is a highly contagious vesicular disease that affects cloven-hoofed animals, causing substantial economic losses to the livestock industry. The causative FMD virus (FMDV) comprises four structural proteins (VP1, VP2, VP3, and VP4) and several non-structural proteins. Among the capsid proteins, VP4 is the most conserved, making it an attractive target as a diagnostic and vaccine antigen, regardless of FMDV serotype. In this study, we attempted to express the VP4 protein N-terminally fused to a glutathione S-transferase (GST) tag in Escherichia coli. Whereas VP0 and VP2 proteins were expressed in the soluble fraction, we failed to detect VP4, even in the insoluble fraction. To investigate the effect of VP4 C-terminal amino acid residues on protein expression, we constructed three VP4 mutants fused to GST, among which the mutant in which the C-terminal 15 amino acid residues had been deleted showed the highest level of protein expression. Furthermore, protein expression was observed even in the mutant in which three amino acid residues (DKK) had been fused to the C terminus. However, unlike the other two mutants, the wild-type VP4 mutant was poorly expressed, thereby indicating that the C-terminal amino acid residues could play a pivotal role in determining expression of the VP4 protein in E. coli.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    Gene cloning
    Prediction of hydrophobicity
    Recombinant protein expression and purification
    SDS-PAGE
    Western blot analysis
RESULTS
DISCUSSION
ACKNOWLEDGEMENTS
REFERENCES

• Sun Young Park(Center for FMD Vaccine Research, Animal and Plant Quarantine Agency)
• Dohyun Kim(Center for FMD Vaccine Research, Animal and Plant Quarantine Agency)
• Sang Hyun Park(Center for FMD Vaccine Research, Animal and Plant Quarantine Agency)
• Jong-Hyeon Park(Center for FMD Vaccine Research, Animal and Plant Quarantine Agency)
• Young-Joon Ko(Center for FMD Vaccine Research, Animal and Plant Quarantine Agency) Corresponding Author