Biotechnology - Synthesis of Therapeutic Agents - Discussion

The P1 sequence encodes the capsid proteins VP4, VP2, VP3, and VP1. Initial processing of the viral polyprotein generates VP0 (a precursor to VP4 and VP2), VP3, and VP1.

Parechoviruses and kobuviruses do not process the P1 capsid precursor in a manner analogous to how poliovirus processes VP0; therefore, complete processing of the capsid proteins results in only three proteins used in the formation of the virion capsid.

For poliovirus, cleavage of the P1 region into the mature capsid components requires the proteolytic activity of 3CD.

For all picornaviruses that process VP0 into VP4 and VP2, an unknown host or viral factor may affect this novel cleavage event.

Please explain.

Please give Explanation.