The twenty-nine amino acid C-terminal cytoplasmic domain of poliovirus 3AB is critical for nucleic acid chaperone activity.
Poliovirus 3AB protein is the first picornavirus protein demonstrated to have nucleic acid chaperone activity. Further characterization of 3AB demonstrates that the C-terminal 22 amino acids (3B region (also referred to as VPg), amino acid 88-109) of the protein is required for chaperone activity, as mutations in this region abrogate nucleic acid binding and chaperone function. Protein 3B alone has no chaperone activity as determined by established assays that include the ability to stimulate nucleic acid hybridization in a primer-template annealing assay, helix-destabilization in a nucleic acid unwinding assay, or aggregation of nucleic acids. In contrast, the putative 3AB C-terminal cytoplasmic domain (C terminal amino acids 81-109, 3B + the last 7 C-terminal amino acids of 3A, termed 3B+7 in this report) possesses strong activity in these assays, albeit at much higher concentrations than 3AB. The characteristics of several mutations in 3B+7 are described here, as well as a model proposing that 3B+7 is the site of the "intrinsic" chaperone activity of 3AB while the 3A N-terminal region (amino acids 1-58) and/or membrane anchor domain (amino acids 59-80) serve to increase the effective concentration of the 3B+7 region leading to the potent chaperone activity of 3AB.
Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA.
Divya R
DR
Gangaramani
Elizabeth L
EL
Eden
Manthan
M
Shah
Jeffrey J
JJ
Destefano
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D003593:Cytoplasm / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D009696:Nucleic Acids / Q000378:metabolism*; D017955:Poliovirus / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication / Q000502:physiology
C520978:3AB protein, poliovirus; D000596:Amino Acids; D008565:Membrane Proteins; D018832:Molecular Chaperones; D009696:Nucleic Acids; D016601:RNA-Binding Proteins; D017361:Viral Nonstructural Proteins