CAPSID ASSEMBLY AND INVOLVED FUNCTION-ANALYSIS OF 12 CORE PROTEIN MUTANTS OF DUCK HEPATITIS-B VIRUS

The roles of different regions of the duck hepatitis B virus (DHBV) co re protein on viral capsid assembly and related functions were examine d. Twelve deletion and insertion mutations which covered 80% of the DH BV C open reading frame were constructed and expressed in Escherichia coli. The N-terminal region (amino acids 3 to 66) of DHBV core protein was important for its tertiary structure and function in E. coli. The expressed core mutants without this region apparently inhibited E. co li growth. The results of transmission electron microscopy off. coli t hin sections, capsid agarose gel, and sucrose gradient sedimentation d emonstrated that a few DHBV core mutants with insertion in the N termi nus and deletion in the C terminus retained the ability to form core-l ike particles in E. coli. However, other mutations in most of N-termin al and central regions strongly inhibited the self-assembly ability of DHBV core protein in E. coil. In addition, the mutant with a C-termin al region deletion (amino acids 181 to 228) lost most of the nucleic a cid-binding activity of the DHBV core protein.