Solution structure and RNA-binding activity of the N-terminal leucine-repeat region of hepatitis delta antigen.
Hepatitis delta virus (HDV) is a satellite virus of the hepatitis B virus (HBV) which provides the surface antigen for the viral coat. The RNA genome of HDV encodes two proteins: the small delta antigen and the large delta antigen. The two proteins resemble each other except for the presence of an additional 19 amino acids at the C terminus of the latter species. We have found that the N-terminal leucine-repeat region of hepatitis delta antigen (HDAg) binds to the autolytic domain of HDV genomic RNA and attenuates its autolytic activity. A 27-residue polypeptide corresponding to residues 24-50 of HDAg, designated dAg(24-50), was synthesized, and its solution structure was found to be an alpha-helix by circular dichroism and (1)H-nuclear magnetic resonance (NMR) techniques. Binding affinity of dAg(24-50) with HDV genomic RNA was found to increase with its alpha-helical content, and it was further confirmed by modifying its N- and C-terminal groups. Furthermore, the absence of RNA binding activity in the mutant peptides, dAgM(24-50am) and dAgM(Ac24-50am), in which Lys38, Lys39, and Lys40 were changed to Glu, indicates a possible involvement of these residues in their binding activity. Structural knowledge of the N-terminal leucine-repeat region of HDAg thus provides a molecular basis for the understanding of its role in the interaction with RNA. Proteins 1999;37:121-129.
Lin
I J
IJ
Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan, ROC.
Lou
Y C
YC
Pai
M T
MT
Wu
H N
HN
Cheng
J W
JW
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D018963:Hepatitis Antigens / Q000737:chemistry*; D003698:Hepatitis Delta Virus / Q000235:genetics*; D035923:Hepatitis delta Antigens; D006801:Humans; D007930:Leucine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D012313:RNA / Q000378:metabolism*; D016415:Sequence Alignment
D018963:Hepatitis Antigens; D035923:Hepatitis delta Antigens; C442244:hepatitis delta virus large antigen; D012313:RNA; D007930:Leucine