[Polymeric forms of the influenza virus nucleoprotein]

Two high-molecular-weight types of in vivo formed nucleoproteins (NP) capable of reacting with anti-NP monoclonal antibodies were detected in continuous MDCK cells and primary CEFs, along with the monomeric virus NP. High-molecular NP were stable at 37 degrees C, despite the presence of dodecyl sulfate and B-mercaptoethanol, but were converted to monomeric NP at 37 degrees C in the presence of 6 M urea, 1 M NaCl, and at acid pH. Hence, high-molecular-weight NP may be the polymeric forms of NP, which are probably stabilized by noncovalent bonds. The kinetics of NP-polymers formation suggests that NP-monomers are their precursors and NP-polymers are formed rapidly after monomeric NP molecules synthesis. Both forms of NP-polymers are detected in the sedimented and soluble fractions of not only cell lysate, but in the extracellular maintenance medium as well. NP-polymers are resistant to RNAse and are more resistant to protease than NP-monomers.