Identification of a second protein encoded by influenza C virus RNA segment 6.
Influenza C virus matrix protein (M1) is encoded by a spliced mRNA derived from RNA segment 6. Unspliced mRNA from this RNA segment, which has not been previously identified, can potentially encode a polypeptide that contains an additional 132 amino acids on the carboxy terminus of the M1 protein. Here the nucleotide sequences of RNA segment 6 of four influenza C strains, isolated in Japan between 1964 and 1988, were compared with the previously determined sequence of C/Ann Arbor/1/50. The results indicated that the deduced amino acid sequence of the carboxy-terminal 132 amino acid domain is conserved fairly well although it is more divergent than the M1 protein sequence. Examination of RNA segment 6-specific mRNAs also showed that unspliced mRNA is present, although in small quantities (approximately 13% of spliced mRNA), in influenza C virus-infected cells. To search for a polypeptide encoded by the unspliced mRNA, the extra carboxy-terminal domain was expressed in Escherichia coli as the glutathione S-transferase fusion protein, and rabbit immune serum was raised against the purified fusion protein. Immunoprecipitation experiments with this antiserum revealed that a previously unrecognized protein of apparent M(r) approximately 18,000, designated CM2, is synthesized in influenza C virus-infected cells.
Hongo
S
S
Department of Bacteriology, Yamagata University School of Medicine, Japan.
Sugawara
K
K
Nishimura
H
H
Muraki
Y
Y
Kitame
F
F
Nakamura
K
K
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005814:Genes, Viral / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics; D009982:Gammainfluenzavirus / Q000235:genetics*; D007564:Japan; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000276:immunology; D017422:Sequence Analysis, DNA; D014763:Viral Matrix Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D014764:Viral Proteins / Q000235:genetics*
C090877:CM2 protein, Influenza C virus; C031540:M-protein, influenza virus; C488936:M1 protein, Influenza A virus; D012333:RNA, Messenger; D012367:RNA, Viral; D011993:Recombinant Fusion Proteins; D014763:Viral Matrix Proteins; D014764:Viral Proteins