Distinct binding sites for zinc and double-stranded RNA in the reovirus outer capsid protein sigma 3.
By atomic absorption analysis, we determined that the reovirus outer capsid protein sigma 3, which binds double-stranded RNA (dsRNA), is a zinc metalloprotein. Using Northwestern blots and a novel zinc blotting technique, we localized the zinc- and dsRNA-binding activities of sigma 3 to distinct V8 protease-generated fragments. Zinc-binding activity was contained within an amino-terminal fragment that contained a transcription factor IIIA-like zinc-binding sequence, and dsRNA-binding activity was associated with a carboxy-terminal fragment. By these techniques, new zinc- and dsRNA-binding activities were also detected in reovirus core proteins. A sequence similarity was observed between the catalytic site of the picornavirus proteases and the transcription factor IIIA-like zinc-binding site within sigma 3. We suggest that the zinc- and dsRNA-binding activities of sigma 3 may be important for its proposed regulatory effects on viral and host cell transcription and translation.
Schiff
L A
LA
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Nibert
M L
ML
Co
M S
MS
Brown
E G
EG
Fields
B N
BN
D000595:Amino Acid Sequence; D001665:Binding Sites; D002213:Capsid / Q000378:metabolism*; D036022:Capsid Proteins; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000378:metabolism*; D016601:RNA-Binding Proteins; D012087:Reoviridae / Q000378:metabolism* / Q000648:ultrastructure; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
D036022:Capsid Proteins; D010446:Peptide Fragments; D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; D014764:Viral Proteins; C053179:sigma protein 3, Reovirus; D010447:Peptide Hydrolases; D015032:Zinc