| With the spread of poxvirus,human society is facing a new round of pandemic threat.The poxvirus genome contains a variety of immunomodulatory molecules that mediate immune escape and tolerance during infection.Poxviruses,especially poxviruses of the genus poxvirus that can infect humans,contain a variety of homologous proteins of human immune regulatory molecules,including tumor necrosis factor receptor-like proteins,cytokine like proteins,etc.In this study,by comparing the genomes of monkeypox virus and vaccinia virus,we found a gene that is highly homologous to human CD47,the poxvirus CD47-like protein.Sequence similarity analysis reveals that the extracellular fragment of this protein is highly conserved in vaccinia virus and monkeypox virus,and the amino acid similarity is 99%.In this study,different expression systems were constructed to explore the preparation of CD47 protein in vitro,and the prokaryotic expression system was used to obtain the poxvirus CD47-like protein.The molecular assembly forms and physicochemical properties were analyzed,and the effects of p H,temperature,REDOX conditions and other factors on protein expression and stability were explored.The binding ability to the ligand of human CD47,SIRP-α,was analyzed by surface plasmon resonance(SPR).We found that poxvirus CD47-like proteins spontaneously form dimers,which are different from the monomeric dominant form of human CD47 molecules.By comparing the binding affinity of CD47-like proteins with human SIRP-α,we found that the binding affinity of CD47-like proteins with human SIRP-α was weak,which was substantially lower than that of human CD47 receptor.Therefore,we speculate that CD47-like proteins in poxviruses may not interfere with the SIRP-α-mediated macrophage inhibition signaling,and there may be other host ligands or receptors involved in the host immune system by interacting with CD47 like protein to promote virus infection.Further comparative study of functional differences between monomer morphology and dimer,and determination of crystal structure of dimer proteins are of great value for our understanding of viral immune regulatory molecules.The analysis of the protein structure and function of CD47-like protein of poxvirus has critical significance for the future study of poxvirus infection and immune escape pathway. |
