N-terminal myristylation of HBV preS1 domain enhances receptor recognition

The N-terminal portion of the large envelope protein of the human hepatitis B virus (HBV), the preS1 domain, plays a fundamental role in cell attachme nt and infectivity. Recent investigations have suggested that myristylation of preS1 Gly(2) residue is essential for viral infectivity, but the import ance of this post-translational modification on HBV-receptor interaction ha s not been elucidated completely. In this study we produced, using stepwise solid-phase chemical synthesis, the entire preS1[1-119] domain (adw2 subty pe), and compared its receptor binding activity with the myristylated form, myristyl-preS1[2-119] in order to define the importance of fatty acid modi fication. Both synthetic proteins were fully characterized in terms of stru ctural identity using TOF-MALDI mass spectrometry and analysis of tryptic f ragments. Circular dichroism measurements indicated a low content of ordere d structure in the preS1 protein, while the propensity of the myristylated derivative to assume a conformationally defined structure was more evident. HBV-receptor binding assays performed with plasma membranes preparations f rom the hepatocyte carcinoma cell line HepG2 clearly showed that the preS1[ 1-119] domain recognizes the HBV receptor, and confirmed that binding is oc curring through the 21-47 region. The myristylated derivative recognized HB V receptor preparations with higher affinity than the preS1 domain, suggest ing that the conformational transitions induced in the preS1 moiety by fatt y acid post-translational modification are important for efficient attachme nt of viral particles to HBV receptors.