C-Terminal carboxyl methylation of a human placental 23 kDa protein catalyzed by membrane-associated methyltransferase has been investigated. The 23 kDa protein substrate methylated was partially purified by DEAE-Sephacel, hydroxyapatite and Sephadex G-100 gel filtration chromatographies. The substrate protein was eluted on Sephadex G-100 gel filtration chromatography as a protein of about 29 kDa. In the absence of Mg2+, the methylation was stimulated by guanine nucleotides (GTP, GDP and GTPgammaS), but in the presence of Mg2+, only GTPgammaS stimulated the methylation which was similar to the effect on the G25K/rhoGDI complex. AFC, an inhibitor of C-terminal carboxyl methylation, inhibited the methylation of human placental 23 kDa protein. These results suggests that the substrate is a small G protein different from the G25K and is methylated on C-terminal isoprenylated cysteine residue. This was also confirmed by vapor phase analysis. The methylated substrate protein was redistributed to membrane after in vitro methylation, suggesting that the methylation of this protein is important for the redistribution of the 23 kDa small G protein for its putative role in intracellular signaling.
Cysteine/metabolism* ; Female ; GTP-Binding Proteins/metabolism* ; Guanine Nucleotides/pharmacology ; Human ; Methylation ; Placenta/metabolism* ; Placenta/enzymology ; Pregnancy ; Pregnancy Proteins/metabolism* ; Protein Methyltransferases/metabolism*

We evaluated the anti-HBV effects of nucleotide analogues, Entecavir (ETV) and Lamivudine (LAM) targeting mouse model of HBV persistent infection with recombinant adeno-associated virus 8 carrying 1.3 copies of HBV genome (rAAV8-1.3HBV). Ninety percent (27 of 30 mice) of rAAVS-treated mice were chosen as mouse model. Four groups were orally administrated with different doses of ETV (1 mg/(kgd) or 0.1 mg/(kgd)) and LAM (500 mg/(kgd) or 100 mg/(kgd)) once a day for 10 days. The other two groups were set as normal saline treated and untreated control. We detected the levels of HBV DNA, HBeAg and HBsAg in sera at different time. Results indicate that HBV DNA level decreased significantly (P < 0.05) in drug-treated groups compared with normal saline group after drug administration. Fifteen days after the drug withdrawal, HBV DNA level rebounded back obviously (P < 0.05) in groups with low doses of ETV and LAM. However, there was no apparent change of HBeAg and HBsAg in the whole process among all groups. These results showed that our model could reflect the anti-viral effect of nucleotide analogues. This model can be a useful and convenient tool for anti-HBV drug discovery.
Animals ; Antiviral Agents ; pharmacology ; Dependovirus ; genetics ; metabolism ; Disease Models, Animal ; Genetic Vectors ; Genome, Viral ; Guanine ; analogs & derivatives ; pharmacology ; Hepatitis B Antibodies ; blood ; Hepatitis B virus ; genetics ; physiology ; Hepatitis B, Chronic ; virology ; Lamivudine ; pharmacology ; Mice ; Mice, Inbred C57BL ; Nucleotides ; pharmacology ; Transduction, Genetic ; Virus Replication