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J. Virol., 09 1996, 5832-5839, Vol 70, No. 9
CF Arias, P Romero, V Alvarez and S Lopez
The infectivity of rotaviruses is increased by and most probably is
dependent on trypsin treatment of the virus. This proteolytic treatment
specifically cleaves VP4, the protein that forms the spikes on the surface
of the virions, to polypeptides VP5 and VP8. This cleavage has been
reported to occur in rotavirus SA114fM at two conserved, closely spaced
arginine residues located at VP4 amino acids 241 and 247. In this work, we
have characterized the VP4 cleavage products of rotavirus SA114S generated
by in vitro treatment of the virus with increasing concentrations of
trypsin and with proteases AspN and alpha- chymotrypsin. The VP8 and VP5
polypeptides were analyzed by gel electrophoresis and by Western blotting
(immunoblotting) with antibodies raised to synthetic peptides that mimic
the terminal regions of VP4 generated by the trypsin cleavage. It was shown
that in addition to arginine residues 241 and 247, VP4 is cleaved at
arginine residue 231. These three sites were found to have different
susceptibilities to trypsin, Arg-241 > Arg-231 > Arg-247, with the
enhancement of infectivity correlating with cleavage at Arg-247 rather than
at Arg-231 or Arg-241. Proteases AspN and alpha-chymotrypsin cleaved VP4 at
Asp- 242 and Tyr-246, respectively, with no significant enhancement of
infectivity, although this enhancement could be achieved by further
treatment of the virus with trypsin. The VP4 end products of trypsin
treatment were a homogeneous VP8 polypeptide comprising VP4 amino acids 1
to 231 and a heterogeneous VP5, which is formed by two polypeptide species
(present at a ratio of approximately 1:5) as a result of cleavage at either
Arg-241 or Arg-247. A pathway for the trypsin activation of rotavirus
infectivity is proposed.
Copyright © 1996, American Society for Microbiology
Trypsin activation pathway of rotavirus infectivity
Departamento de Genetica y Fisiologia Molecular, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos, Mexico. arias@ibt.unam.mx
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