Structural basis for ubiquitin-like ISG 15 protein binding to the NS1 protein of influenza B virus: a protein-protein interaction function that is not shared by the corresponding N-terminal domain of the NS1 protein of influenza A virus.
The N-terminal domains of the NS1 protein of influenza B virus (NS1B protein) and the NS1 protein of influenza A virus (NS1A protein) share one function: binding double-stranded RNA (dsRNA). Here we show that the N-terminal domain of the NS1B protein possesses an additional function that is not shared by its NS1A counterpart: binding the ubiquitin-like ISG15 protein that is induced by influenza B virus infection. Homology modeling predicts that the dimeric six-helical N-terminal domain of the NS1B protein differs from its NS1A protein counterpart in containing large loops between helices 1 and 2 (loops 1 and 1') and between helices 2 and 3 (loops 2 and 2'). Mutagenesis establishes that residues located in loop 1/1' together with residues located in polypeptide segment 94-103 form the ISG15 protein-binding site of NS1B protein. Loop 1/1' is not required for dsRNA binding, which instead requires arginine residues R50, R53, R50', and R53' located in antiparallel helices 1 and 1'. Further, we demonstrate that the binding sites for RNA and protein are independent of each other. In particular, ISG15 and dsRNA can bind simultaneously; the binding of the ISG15 protein does not have a detectable effect on the binding of dsRNA, and vice versa.
Yuan
Weiming
W
Institute for Cellular and Molecular Biology, Section of Molecular Genetics and Microbiology, University of Texas at Austin, 78712, USA.
Aramini
James M
JM
Montelione
Gaetano T
GT
Krug
Robert M
RM
D000595:Amino Acid Sequence; D001665:Binding Sites; D016207:Cytokines / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D009981:Influenza B virus / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D012367:RNA, Viral / Q000378:metabolism; D014452:Ubiquitins / Q000031:analogs & derivatives*; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000378:metabolism
D016207:Cytokines; C085820:INS1 protein, influenza virus; D012367:RNA, Viral; D014452:Ubiquitins; D017361:Viral Nonstructural Proteins; C074034:ISG15 protein, human