Crystal Structure and Proteomics Analysis of Empty Virus-like Particles of Cowpea Mosaic Virus

• Published in: Structure (London) 2016-04, Vol.24 (4), p.567-575
• Main Authors: Huynh, Nhung T., Hesketh, Emma L., Saxena, Pooja, Meshcheriakova, Yulia, Ku, You-Chan, Hoang, Linh T., Johnson, John E., Ranson, Neil A., Lomonossoff, George P., Reddy, Vijay S.
• Format: Article
• Language: English
• Subjects: Capsid Proteins - chemistry; Capsid Proteins - metabolism; Cleavage; Comovirus - chemistry; Comovirus - metabolism; Cowpea mosaic virus; Cowpeas; CPMV; Cryoelectron Microscopy; Crystal structure; Crystallography, X-Ray - methods; eVLPs; Mass Spectrometry; Models, Molecular; Mosaics; Protein Structure, Secondary; Proteolysis; proteomic; Proteomics; Proteomics - methods; Reagents; structure; Viral Proteins - chemistry; Viral Proteins - metabolism; Virion - chemistry; Virion - metabolism; Viruses; X-rays
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2016.02.011

Empty virus-like particles (eVLPs) of Cowpea mosaic virus (CPMV) are currently being utilized as reagents in various biomedical and nanotechnology applications. Here, we report the crystal structure of CPMV eVLPs determined using X-ray crystallography at 2.3 Å resolution and compare it with previously reported cryo-electron microscopy (cryo-EM) of eVLPs and virion crystal structures. Although the X-ray and cryo-EM structures of eVLPs are mostly similar, there exist significant differences at the C terminus of the small (S) subunit. The intact C terminus of the S subunit plays a critical role in enabling the efficient assembly of CPMV virions and eVLPs, but undergoes proteolysis after particle formation. In addition, we report the results of mass spectrometry-based proteomics analysis of coat protein subunits from CPMV eVLPs and virions that identify the C termini of S subunits undergo proteolytic cleavages at multiple sites instead of a single cleavage site as previously observed. •The crystal structure of eVLPs is extremely similar to that of CPMV virions•After assembly, the C termini of S subunits undergo proteolysis at multiple sites•Varied composition of processed S subunits ensues slow and fast electrophoretic forms The crystal structure and proteomics analysis of empty virus-like particles (eVLPs) of Cowpea mosaic virus (CPMV) reported by Huynh et al. reveals the structural congruity with the virions and diverse composition of processed S subunits of a bionanoparticle that is used in vaccine development, in vivo imaging, drug delivery, and other nanotechnology applications.