Vaccinia viral protein A27 is anchored to the viral membrane via a cooperative interaction with viral membrane protein A17.
The vaccinia viral protein A27 in mature viruses specifically interacts with heparan sulfate for cell surface attachment. In addition, A27 associates with the viral membrane protein A17 to anchor to the viral membrane; however, the specific interaction between A27 and A17 remains largely unclear. To uncover the active binding sites and the underlying binding mechanism, we expressed and purified the N-terminal (18-50 residues) and C-terminal (162-203 residues) fragments of A17, which are denoted A17-N and A17-C. Through surface plasmon resonance, the binding affinity of A27/A17-N (KA = 3.40 × 10(8) m(-1)) was determined to be approximately 3 orders of magnitude stronger than that of A27/A17-C (KA = 3.40 × 10(5) m(-1)), indicating that A27 prefers to interact with A17-N rather than A17-C. Despite the disordered nature of A17-N, the A27-A17 interaction is mediated by a specific and cooperative binding mechanism that includes two active binding sites, namely (32)SFMPK(36) (denoted as F1 binding) and (20)LDKDLFTEEQ(29) (F2). Further analysis showed that F1 has stronger binding affinity and is more resistant to acidic conditions than is F2. Furthermore, A27 mutant proteins that retained partial activity to interact with the F1 and F2 sites of the A17 protein were packaged into mature virus particles at a reduced level, demonstrating that the F1/F2 interaction plays a critical role in vivo. Using these results in combination with site-directed mutagenesis data, we established a computer model to explain the specific A27-A17 binding mechanism.
Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529.
Da-Rong
DR
Wang
Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529.
Jye-Chian
JC
Hsiao
Department of Applied Chemistry, National Chia-Yi University, Chia-Yi, 60004, Taiwan, Republic of China.
Chien-Hsuan
CH
Wong
Department of Applied Chemistry, National Chia-Yi University, Chia-Yi, 60004, Taiwan, Republic of China.
Guo-Chian
GC
Li
Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529.
Su-Ching
SC
Lin
Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529.
Steve S-F
SS
Yu
Department of Applied Chemistry, National Chia-Yi University, Chia-Yi, 60004, Taiwan, Republic of China.
Wenlung
W
Chen
Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529.
Wen
W
Chang
Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529. Electronic address: tzougate@gate.sinica.edu.tw.
Der-Lii M
DM
Tzou
D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003198:Computer Simulation; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C081257:A17L protein, Vaccinia virus; C526377:A27 protein, vaccinia virus; D002352:Carrier Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins
Pox Viruses; Protein Structure; Protein-Protein Interactions; Viral Protein; Virus Assembly