The nucleocapsid protein is referred to as NP. NP is is the major structural component of the nucleocapsid. The protein is approx. 58 kDa. 2600 NP molecules go to tightly encapsidate the RNA. NP interacts with several other viral encoded proteins, all of which are involved in controlling replication. {NP-NP, NP-P, NP-(PL), and NP-V}.