Affiliation:
1. Department of Biochemistry, Molecular Biology, and Cell Biology,1
2. Department of Neurobiology and Physiology,2 and
3. Howard Hughes Medical Institute,3Northwestern University, Evanston, Illinois 60208-3500
Abstract
ABSTRACT
The M
2
protein of influenza A virus forms a proton channel that is required for viral replication. The M
2
ion channel is a homotetramer and has a 24-residue N-terminal extracellular domain, a 19-residue transmembrane domain, and a 54-residue cytoplasmic tail. We show here that the N-terminal methionine residue is cleaved from the mature protein. Translational stop codons were introduced into the M
2
cDNA at residues 46, 52, 62, 72, 77, 82, 87, and 92. The deletion mutants were designated trunc
x
, according to the amino acid position that was changed to a stop codon. We studied the role of the cytoplasmic tail by measuring the ion channel activity (the current sensitive to the M
2
-specific inhibitor amantadine) of the cytoplasmic tail truncation mutants expressed in oocytes of
Xenopus laevis
. When their conductance was measured over time, mutants trunc72, trunc77, and trunc92 behaved comparably to wild-type M
2
protein (a decrease of only 4% over 30 min). In contrast, conductance decreased by 28% for trunc82, 27% for trunc62, and 81% for trunc52 channels. Complete closure of the channel could be observed in some cells for trunc62 and trunc52 within 30 min. These data suggest that a role of the cytoplasmic tail region of the M
2
ion channel is to stabilize the pore against premature closure while the ectodomain is exposed to low pH.
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
Cited by
63 articles.
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