To derive structural information about the vesicular stomatitis virus (VSV)
nucleocapsid (N) protein, the N protein and the VSV phosphoprotein (P prot
ein) were expressed together in Escherichia coli, The N and P proteins form
ed soluble protein complexes of various molar ratios when coexpressed. The
major N/P protein complex was composed of 10 molecules of the N protein, 5
molecules of the P protein, and an RNA, A soluble N protein-RNA oligomer fr
ee of the P protein was isolated from the N/P protein-RNA complex using con
ditions of lowered pH. The molecular weight of the N protein-RNA oligomer,
513,879, as determined by analytical ultracentrifugation, showed that it wa
s composed of 10 molecules of the N protein and an RNA of approximately 90
nucleotides. The N protein-RNA oligomer had the appearance of a disk with o
uter diameter, inner diameter, and thickness of 148 +/- 10 Angstrom, 78 +/-
9 Angstrom, and 83 +/- 8 Angstrom, respectively, as determined by electron
microscopy, RNA in the complexes was protected from RNase digestion and wa
s stable at pH 11. This verified that N/P protein complexes expressed in E.
coli were competent for encapsidation, In addition to coexpression with th
e full-length P protein, the N protein was expressed with the C-terminal 72
amino acids of the P protein. This portion of the P protein was sufficient
for binding to the N protein, maintaining it in a soluble state, and for a
ssembly of N protein-RNA oligomers. With the results provided in this repor
t, we propose a model for the assembly of an N/P protein-RNA oligomer.