Purification and characterization of the reovirus cell attachment protein sigma 1.
It has previously been shown that of all the soluble reovirus-specified proteins present in the infected cell lysate, protein sigma 1 alone possesses the capacity to bind to host cells (P.W.K. Lee, E.C. Hayes, and W.K. Joklik, 1981, Virology 108, 156-163). We found that sigma 1 from urea-disrupted reovirus particles was also capable of such specific binding. Reovirions were therefore used as a source of functional sigma 1. Accordingly, a simple procedure has been developed to purify sigma 1 by subjecting urea-disrupted reovirions to DEAE ion-exchange chromatography. Protein sigma 1 thus isolated was electrophoretically homogeneous and the recovery was estimated to be 50 to 60% of the theoretical yield. The purified protein presumably maintained its native conformation since it was recognized by a panel of monoclonal anti-sigma 1 antibodies previously isolated, and was capable of specifically binding to host cell receptors, agglutinating human erythrocytes and inducing neutralization and hemagglutination-inhibition antibodies. Subsequent chemical crosslinking studies revealed the presence of oligomeric (mostly dimeric) sigma 1 forms in the preparation. The amino acid composition of the purified sigma 1 was found to closely match that inferred from the S1 gene sequence. However, attempts to determine its amino-terminal sequence have not been successful. The p/ of the purified protein was determined to be 6.8. Circular dichroic measurements of the purified sigma 1 indicated that 54 and 19% of its residues were arranged in alpha-helical and beta-sheet secondary structures, respectively.
D000596:Amino Acids / Q000032:analysis; D036022:Capsid Proteins; D002942:Circular Dichroism; D006389:Hemagglutinins, Viral / Q000276:immunology / Q000302:isolation & purification*; D046911:Macromolecular Substances; D012089:Mammalian orthoreovirus 3 / Q000032:analysis*; D011487:Protein Conformation; D012087:Reoviridae / Q000032:analysis*; D014764:Viral Proteins / Q000276:immunology / Q000302:isolation & purification*; D014771:Virion / Q000032:analysis / Q000302:isolation & purification
D000596:Amino Acids; D036022:Capsid Proteins; D006389:Hemagglutinins, Viral; D046911:Macromolecular Substances; D014764:Viral Proteins; C031728:sigma 1 protein, reovirus