Structure-Based Insight on the Mechanism of N-Glycosylation Inhibition by Tunicamycin.

N-glycosylation, a common post-translational modification, is widely acknowledged to have a significant effect on protein stability and folding. N-glycosylation is a complex process that occurs in the endoplasmic reticulum (ER) and requires the participation of multiple enzymes. GlcNAc-1-P-transferase (GPT) is essential for initiating N-glycosylation in the ER. Tunicamycin is a natural product that inhibits N-glycosylation and produces ER stress, and thus it is utilized in research. The molecular mechanism by which GPT triggers N-glycosylation is discussed in this review based on the GPT structure. Based on the structure of the GPT-tunicamycin complex, we also discuss how tunicamycin reduces GPT activity, which prevents N-glycosylation. This review will be highly useful for understanding the role of GPT in the N-glycosylation of proteins, as well as presents a potential for considering tunicamycin as an antibiotic treatment.

[Genotypes of hepatitis B virus on Jeju island].

BACKGROUND/AIMS: Hepatitis B virus (HBV) was classified into 8 genotypes by a sequence divergence in the entire genome designated from A to H. HBV genotypes have distinct geographic distributions. Recently, HBV genotypes have been partially found as influencing the clinical manifestation of chronic liver disease in hosts. In Korea, the distribution of HBV genotypes remains unclear. The aim of this study was to evaluate the prevalence of the HBV genotype on Jeju Island. METHODS: Hepatitis B virus genotypes were evaluated among 107 hepatitis B carriers residing on Jeju Island. We used single PCR and multiplex-PCR assay with genotype-specific primer pairs for HBV genotypes A-F for the genotyping. RESULTS: 1. Fifty nine samples (55%) were positive for HBV DNA. The positivity was different according to the pattern of HBeAg/ anti-HBe expression, as -/-; 2/3 (66.7%), -/+; 30/73 (30%), +/-; 24/28 (85.7%) and +/+; 3/3 (100%). 2. In the single primer set of genotype-specific PCR, 59 samples (100%) were detected as genotype C and 2 (3%) were also detected as genotype A and B. 3. In multiplex-PCR, 58 samples (98%) were detected as genotype C and only one (2%) as a mixed pattern of genotype B and C. 4. When the PCR products were amplified with universal sense and genotype specific anti-sense from one genotype A, one B, and 2 C, all were included in genotype C. CONCLUSIONS: These results suggest that on Jeju Island, almost all HBV genotypes are C.