Abstract: | Antibodies specific to the N-terminal 34-aminoacid peptide of the major nucleocapsid protein NP of human influenza A viruses were obtained. The NP proteolytic cleavage occurring in infected cells late in infection has been demonstrated using this antibody. The antibody specifically reacted with noncleaved NP of 56 kD m.w. but not with cleaved NP of 53 kD m.w. This indicates that NP56-->NP53 intracellular cleavage released the N-terminal 3 kD peptide of Np molecule. The released 3 kD peptide did not accumulate in infected cells. Since the RNA-binding and nucleus migrating signals are located in the N-terminus of NP molecule, presumably, the terminal cleavage is important for intracellular NP functions. |