Proteolytic Processing of the Astrovirus Capsid

AUTOR(ES)

Bass, D. M.

FONTE

American Society for Microbiology

RESUMO

To further characterize the nature of proteolytic processing of the astrovirus capsid, we infected Caco-2 cells with a high multiplicity of astrovirus without trypsin in the presence of 5 to 10% fetal calf serum. These infections were characterized by pulse-chase labeling with [35S]methionine, electron microscopy, gel electrophoresis of purified viral particles, and analysis of infectivity of such particles with and without added trypsin. Pulse-chase experiments showed that the astrovirus capsid protein was initially translated as an approximately 87-kDa protein. The 87-kDa capsid protein was rapidly converted intracellularly to a 79-kDa form which was found in smaller amounts in the cell supernatant. Purification by differential centrifugation yielded particles that appeared quite similar to trypsin-grown astrovirus particles by negatively stained electron microscopy. These particles were antigenically distinct from trypsin-treated virions as demonstrated by their various reactions with monoclonal antibodies in a solid-phase immunoassay. The purified trypsin-free particles were mainly composed of the 79-kDa capsid protein which was found to have an amino terminus at residue 71 of the entire open reading frame 2 (ORF2) product. The cleavage site was identified in a highly conserved region of the astrovirus ORF2 product. These trypsin-free particles were minimally infectious in cultured Caco-2 cells but became highly infectious (105-fold increase) after trypsin but not chymotrypsin treatment. This trypsin-enhanced infectivity correlated with conversion of the 79-kDa capsid protein to three smaller peptides of approximately 34, 29, and 26 kDa.

Documentos Relacionados

• Proteolytic Processing of a Serotype 8 Human Astrovirus ORF2 Polyprotein
• Maturation of giardiavirus capsid protein involves posttranslational proteolytic processing by a cysteine protease.
• Myristoylation of the poliovirus polyprotein is required for proteolytic processing of the capsid and for viral infectivity.
• Human rhinovirus 2: complete nucleotide sequence and proteolytic processing signals in the capsid protein region.
• Processing of Nonstructural Protein 1a of Human Astrovirus