RESUMO
The Coronavirus Disease 2019 (COVID-19) is a new viral infection caused by the severe acute respiratory coronavirus 2 (SARS-CoV-2). Genomic analyses have revealed that SARS-CoV-2 is related to Pangolin and Bat coronaviruses. In this report, a structural comparison between the Sars-CoV-2 Envelope and Membrane proteins from different human isolates with homologous proteins from closely related viruses is described. The analyses here reported show the high structural similarity of Envelope and Membrane proteins to the counterparts from Pangolin and Bat coronavirus isolates. However, the comparisons have also highlighted structural differences specific of Sars-CoV-2 proteins which may be correlated to the cross-species transmission and/or to the properties of the virus. Structural modelling has been applied to map the variant sites onto the predicted three-dimensional structure of the Envelope and Membrane proteins.
Assuntos
Betacoronavirus/química , Infecções por Coronavirus/virologia , Pneumonia Viral/virologia , Proteínas do Envelope Viral/química , Proteínas da Matriz Viral/química , Alphacoronavirus/química , Alphacoronavirus/classificação , Alphacoronavirus/genética , Sequência de Aminoácidos , Animais , Betacoronavirus/classificação , Betacoronavirus/genética , COVID-19 , Quirópteros/virologia , Coronaviridae/química , Coronaviridae/classificação , Coronaviridae/genética , Proteínas do Envelope de Coronavírus , Eutérios/virologia , Humanos , Modelos Moleculares , Pandemias , Conformação Proteica , SARS-CoV-2 , Homologia de Sequência de Aminoácidos , Especificidade da Espécie , Homologia Estrutural de Proteína , Proteínas do Envelope Viral/genética , Proteínas da Matriz Viral/genéticaRESUMO
A swine acute diarrhea syndrome coronavirus (SADS-CoV) that causes severe diarrhea in suckling piglets was identified in Southern China in 2017. To develop an antigen that is specific, sensitive, and easy to prepare for serological diagnosis, antigenic sites in the SADS-CoV nucleocapsid (N) protein were screened. We generated and characterized an N-reactive monoclonal antibody (mAb) 3E9 from mice immunized with recombinant N protein. Through fine epitope mapping of mAb 3E9 using a panel of eukaryotic-expressed polypeptides with GFP-tags, we identified the motif 343DAPVFTPAP351 as the minimal unit of the linear B-cell epitope recognized by mAb 3E9. Protein sequence alignment indicated that 343DAPVFTPAP351 was highly conserved in different SADS-CoV strains and SADS-related coronaviruses from bat, with one substitution in this motif in HKU2-related bat coronavirus. Using mAb 3E9, we observed that N protein was expressed in the cytoplasm and was in the nucleolus during SADS-CoV replication. N protein was immunoprecipitated from SADS-CoV-infected Vero E6 cells. Taken together, our results indicated that 3E9 mAb could be a useful tool to investigate the structure and function of N protein during viral replication.