A functional GTP-binding motif is necessary for antiviral activity of Mx proteins.
Mx proteins are interferon-induced GTPases that inhibit the multiplication of certain negative-stranded RNA viruses. However, it has been unclear whether GTPase activity is necessary for antiviral function. Here, we have introduced mutations into the tripartite GTP-binding consensus elements of the human MxA and mouse Mx1 proteins. The invariant lysine residue of the first consensus motif, which interacts with the beta- and gamma-phosphates of bound GTP in other GTPases, was deleted or replaced by methionine or alanine. These Mx mutants and appropriate controls were then tested for antiviral activity, GTP-binding capacity, and GTPase activity. We found a direct correlation between the GTP-binding capacities and GTP hydrolysis activities of the purified Mx mutants in vitro and their antiviral activities in transfected 3T3 cells, demonstrating that a functional GTP-binding motif is necessary for virus inhibition. Our results, thus, firmly establish antiviral activity as a novel function of a GTPase, emphasizing the enormous functional diversity of GTPase superfamily members.
Pitossi
F
F
Department of Virology, University of Freiburg, Germany.
Blank
A
A
Schröder
A
A
Schwarz
A
A
Hüssi
P
P
Schwemmle
M
M
Pavlovic
J
J
Staeheli
P
P
D016475:3T3 Cells; D000818:Animals; D000998:Antiviral Agents; D001483:Base Sequence; D016384:Consensus Sequence; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D020558:GTP Phosphohydrolases / Q000737:chemistry; D019204:GTP-Binding Proteins / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D064547:Myxovirus Resistance Proteins; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D014762:Viral Interference
D000998:Antiviral Agents; D017931:DNA Primers; C579071:MX1 protein, human; C579070:Mx1 protein, mouse; D064547:Myxovirus Resistance Proteins; D009838:Oligodeoxyribonucleotides; D011506:Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins