Biology Reference
In-Depth Information
Fig. 1.
The genomic organization of hepatitis viruses.
-ends. It codes
for four overlapping reading frames (ORFs) required for expression of
seven different proteins. The S and C ORFs encode the surface (enve-
lope) and nucleocapsid (core) proteins, respectively (Fig. 1B). The 'P'
ORF codes for the viral polymerase and the 'X' ORF codes for the
regulatory HBx protein. The surface protein is of three types viz.:
small (HBsAg), middle (MHBsAg) and large (LHBsAg). While
HBsAg is the major constituent of all HBV particles and is manufac-
tured in large quantities, the other forms are also present in the virus
particles in varying amounts. The LHBsAg appears to bind the recep-
tor present on liver cells.
held in a circular configuration by base pairing at the 5
′
Hepatitis C Virus
HCV belongs to the family
Flaviviridae
and has a positive sense RNA
genome of approximately 9500 nucleotides. The whole genome
encodes a large polyprotein of about 3000 amino acids. When cleaved
by viral and host proteases the HCV polyprotein produces 10 differ-
ent polypeptides with various biochemical and structural functions.
