FIG. 2.

Proposed functional domains of the astrovirus coat protein. The coat protein is illustrated with the conserved region in the first half (heavily shaded) and the variable region in the last half (no shading) of the molecule. The positively charged N terminus of the coat protein proposed to be involved in viral RNA packaging is indicated (+++) along with the approximate location of trypsin cleavage sites (T▾) and putative caspase cleavage site(s) (C▾). Based on the structural predictions outlined in the text, we propose that the conserved region of the coat protein encodes the assembly domain (AD) required to form the viral capsid and encapsidate the viral RNA whereas the variable region encodes the receptor-interaction domain (RID) that binds to specific receptors on the surface of the host cell.