This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Yang, S Q Articles by Standring, D N Search for Related Content PubMed PubMed Citation Articles by Yang, S Q Articles by Standring, D N

Hepatitis B virus p25 precore protein accumulates in Xenopus oocytes as an untranslocated phosphoprotein with an uncleaved signal peptide.

Hormone Research Institute, University of California, San Francisco 94143-0534.

ABSTRACT

We have analyzed the translocation of hepatitis B virus (HBV) precore (PC) proteins by using Xenopus oocytes injected with a synthetic PC mRNA. The PC region is a 29-amino-acid sequence that precedes the 21.5-kDa HBV capsid or core (C) protein (p21.5) and directs the secretion of core-related proteins. The first 19 PC amino acids provide a signal peptide that is cleaved with the resultant translocation of a 22.5-kDa species (p22.5), in which the last 10 PC residues precede the complete p21.5 C polypeptide. Most p22.5 is matured to 16-20 kDa species by carboxyl-terminal proteolytic cleavage prior to secretion. Here we show that some four unexpected PC proteins of 24 to 25 kDa are produced in addition to the secretion products described above. Protease protection and membrane cosedimentation experiments reveal that all PC proteins behave as expected for proteins that are translocated into the lumen of the endoplasmic reticulum except for the single largest PC protein (p25), which is not translocated. Like p21.5, p25 is a phosphoprotein that localizes to the oocyte cytosol and nucleus, and protease digestion studies suggest that the two molecules have similar two-domain structures. Radiosequencing of immobilized p25 demonstrates that it contains the intact PC signal peptide and represents the unprocessed translation product of the entire PC/C locus. Thus, while many HBV PC protein molecules are correctly targeted to intracellular membranes and translocated, a significant fraction of these molecules can evade translocation and processing.

This article has been cited by other articles:

• Kimura, T., Ohno, N., Terada, N., Rokuhara, A., Matsumoto, A., Yagi, S., Tanaka, E., Kiyosawa, K., Ohno, S., Maki, N. (2005). Hepatitis B Virus DNA-negative Dane Particles Lack Core Protein but Contain a 22-kDa Precore Protein without C-terminal Arginine-rich Domain. J. Biol. Chem. 280: 21713-21719 [Abstract] [Full Text]