The C-terminal half of the preS1 region is essential for the secretion of human hepatitis B virus large S protein devoid of the N-terminal retention sequence.
A large surface protein of human hepatitis B virus was expressed from a mutated S gene in which both the reported retention sequence (aa 2-19) and the C-terminal half of the preS1 region (aa 66-117) were deleted. This retention sequence-free protein was not secreted from the monkey kidney cell line COS-M6 in transient expression assays. When this large S protein was overexpressed in the presence of the major S protein, the secretion of the latter was severely inhibited. Moreover, the presence of S protein in large abundance did not facilitate the secretion of the mutated large S protein at all, indicating that it was subject to more profound retention than the wild-type large S protein. The findings that, like the wild-type large S protein, this altered protein retained some of the properties of its C-terminal S domain, and that the preS1 region was still on its surface suggested that there was no extensive alteration of the polypeptide folding. The interpretation is favored that the C-terminal half of the preS1 region plays a crucial role in the secretion of the large S protein when its N-terminal retention sequence is not present.
Yu
X M
XM
Shanghai Institute of Biochemistry, Academia Sinica, People's Republic of China.
D000818:Animals; D002460:Cell Line; D005814:Genes, Viral; D006514:Hepatitis B Surface Antigens / Q000032:analysis / Q000235:genetics*; D006515:Hepatitis B virus / Q000235:genetics*; D008970:Molecular Weight; D016296:Mutagenesis; D010957:Plasmids; D011498:Protein Precursors / Q000235:genetics*; D014162:Transfection; D014764:Viral Proteins / Q000032:analysis / Q000235:genetics*
D006514:Hepatitis B Surface Antigens; D011498:Protein Precursors; D014764:Viral Proteins