Previous Article | Next Article ![]()
Journal of Virology, January 1999, p. 46-50, Vol. 73, No. 1
Department of
Bacteriology1 and
Department of
Nursing,2 Yamagata University School of
Medicine, Iida-Nishi, Yamagata 990-2331, Japan
Received 1 July 1998/Accepted 8 October 1998
Although unspliced mRNA from influenza C virus RNA segment 6 (M
gene) has a single open reading frame capable of encoding a
374-amino-acid protein (Mr, 42,000), the major
polypeptide synthesized from this mRNA species is the CM2 protein, with
an Mr of 18,000. The present study was
performed to investigate the mechanism by which CM2 is generated
from the unspliced mRNA. It was reported previously that the
374-amino-acid protein (P42) is an integral membrane protein having two
internal hydrophobic domains, one of which (residues 241 to 252) is
followed by two sequences (252 Ile-Thr-Ser and 257 Ala-Ser-Ala)
favorable for cleavage by signal peptidase. To examine the possibility
that P42 is cleaved by signal peptidase after Ser residue 254 or Ala
residue 259 to yield CM2, we constructed three mutated M gene cDNAs in
which either or both of the two sequences were eliminated and tested
their ability to synthesize CM2 in the transfected COS cells. The
results showed that CM2 synthesis was blocked completely when the
second recognition motif for signal peptidase was removed. It was also
found that when the mRNA transcript of the wild-type M gene was
translated in vitro, P42, but not CM2, was synthesized in the absence
of dog pancreas microsomal membranes, whereas CM2, in addition
to a polypeptide (designated M1') slightly larger than matrix protein (M1), was synthesized in the presence of microsomes. When the same
experiment was done with the transcript of the mutated M gene in which
the second recognition motif was removed, synthesis of CM2 could not be
seen, even in the presence of microsomes. From these results,
we conclude that cleavage of P42 by signal peptidase after Ala residue
259 produces CM2, composed of the C-terminal 115 amino acids, in
addition to M1', composed of the N-terminal 259 amino acids.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Influenza C Virus CM2 Protein Is Produced from a 374-Amino-Acid
Protein (P42) by Signal Peptidase Cleavage
*
Corresponding author. Mailing address: Department of
Bacteriology, Yamagata University School of Medicine, Iida-Nishi,
Yamagata 990-2331, Japan. Phone: 81 236 28 5247. Fax: 81 236 28 5250.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»