In order to study whether there is a direct interaction between the key variant gene(AP-PV-YN-Mut)protein of atypical porcine pestivirus(APPV)Yunnan strain and the host protein signal sequence receptor subunit 4(SSR4),the physical and chemical properties,spatial structure and subcellular localization of SSR4 protein were analyzed and predicted using online software such as ProtParam,PredictProtein and TMHMM.The recombinant vectors pCMV-Tag4A-SSR4 and pET-GST-Mut were constructed for GST pull-down test in vitro.The recombinant vectors pBiFC-VN173-SSR4 and pBiFC-VC155-Mut were constructed and the bimolecular fluorescence comple-mentary test(BiFC)was performed in cells to verify whether there was direct interaction between APPV-YN-Mut and host protein SSR4 in vitro and in cells.The results showed that SSR4 protein was a hydrophobic stable protein with no transmembrane structure and signal peptide.The second-ary structure was mainly irregular curl,and the tertiary structure was stable,mainly located in the endoplasmic reticulum.GST pull-down and BiFC experiments showed that APPV-YN-Mut interac-ted directly with host protein SSR4 in vitro and in cells.

In order to study whether there is a direct interaction between the key variant gene(AP-PV-YN-Mut)protein of atypical porcine pestivirus(APPV)Yunnan strain and the host protein signal sequence receptor subunit 4(SSR4),the physical and chemical properties,spatial structure and subcellular localization of SSR4 protein were analyzed and predicted using online software such as ProtParam,PredictProtein and TMHMM.The recombinant vectors pCMV-Tag4A-SSR4 and pET-GST-Mut were constructed for GST pull-down test in vitro.The recombinant vectors pBiFC-VN173-SSR4 and pBiFC-VC155-Mut were constructed and the bimolecular fluorescence comple-mentary test(BiFC)was performed in cells to verify whether there was direct interaction between APPV-YN-Mut and host protein SSR4 in vitro and in cells.The results showed that SSR4 protein was a hydrophobic stable protein with no transmembrane structure and signal peptide.The second-ary structure was mainly irregular curl,and the tertiary structure was stable,mainly located in the endoplasmic reticulum.GST pull-down and BiFC experiments showed that APPV-YN-Mut interac-ted directly with host protein SSR4 in vitro and in cells.