Membrane permeability induced by hepatitis A virus proteins 2B and 2BC and proteolytic processing of HAV 2BC.

The ability to rearrange membranes is a unique feature of nonstructural proteins 2B, 2C, and 2BC of some picornaviruses. To analyze in detail membrane binding of the respective proteins of hepatitis A virus (HAV), they were transiently expressed in the vaccinia/T7 system, and their effect on membrane permeability was studied using beta-galactosidase as reporter. Although 2C had no effect, the significantly increased reporter activity observed in the extracellular space of 2B- and 2BC-expressing cells points to a specific effect of HAV proteins 2B and 2BC on membrane permeability. In biochemical fractionation studies, HAV 2C and 2BC showed properties of intregral membrane proteins, whereas 2B was associated with membranes as a peripheral protein. Proteinase 3C-mediated cleavage of precursor 2BC in vivo was most efficient when the enzyme was coexpressed in its precursor forms P3 or 3ABC, which both include the membrane-anchoring domain 3A. 3ABC showed the same solubility pattern as 2BC, suggesting that colocalization of 2BC and 3ABC might be required for the efficient liberation of 2B and 2C and occurs on membranes that have been proposed as the site of viral RNA replication.