Kaposi's sarcoma-associated herpesvirus (KSHV) vOX2 is a cell surface glycoprotein expressed during viral lytic replication to suppress host inflammatory reactions. Here we have characterised vOX2 with biochemical, biophysical and bioinformatics tools and as a result propose a 3-dimensional model for vOX2 based on structural and functional homology with the PD-L1 protein. To validate this model, vOX2 was characterised by analytical ultracentrifugation (AUC) and circular dichroism spectroscopy (CD). The results identified the potential glycosylation sites and revealed that vOX2 is predominantly a beta-folded molecule with an RGD adhesion motif exposed on the C-terminal domain. The protein exists in monomer-dimer equilibrium similar to its IgV-type folded homologues, with 30-36% glycosylation and the molecular weight of the extracellular fragment of molecule is 32.0-33.6. kDa, much less than 50. kDa. Thus, the structural similarity to PD-L1 verifies its immunomodulatory potential and the RGD motif suggests an adhesive capacity.
Bibliographical noteFunding Information:
The authors acknowledge the helpful contribution of Dr. Christine Milburn (University of St Andrews) for her work in performing PNGase digestions. This work was funded by grants to D.J.B. from the Medical Research Council (MRC; G0400408 and G0800154 ), BBSRC ( BBS/B/14442 ), and CR UK ( C7934 ). The authors acknowledge the support of the Vice Chancellor of Research, Mashhad University of Medical Sciences , Mashhad, Iran (Grant no: MUMS 900118 ).
- Homology modelling
- RGD domain