Membrane Glycoproteins/chemical synthesis; Models, Molecular; Protein Engineering; Recombinant Fusion Proteins/chemical synthesis; Repetitive Sequences, Amino Acid; Severe acute respiratory syndrome-related coronavirus/chemistry; Severe acute respiratory syndrome-related coronavirus/genetics; Viral Envelope Proteins/chemical synthesis; Viral Fusion Proteins/chemical synthesis; Amino Acid Sequence; Binding Sites/genetics; Computer Simulation; Genetic Vectors/chemical synthesis; Membrane Glycoproteins/genetics; Molecular Sequence Data; Murine hepatitis virus/chemistry; Murine hepatitis virus/genetics; Murine hepatitis virus/pathogenicity; Peptide Fragments/biosynthesis; Peptide Fragments/chemistry; Peptide Fragments/genetics; Peptides/chemistry; Peptides/genetics; Peptides/metabolism; Protein Binding/genetics; Protein Engineering/methods; Protein Structure, Secondary/genetics; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Repetitive Sequences, Amino Acid/genetics; Severe acute respiratory syndrome-related coronavirus/pathogenicity; Solubility; Spike Glycoprotein, Coronavirus; Structural Homology, Protein; Viral Envelope Proteins/genetics; Viral Fusion Proteins/genetics; Viral Fusion Proteins/metabolism