Proline-138 is essential for the assembly of hepatitis B virus core protein.

Abstract

In small RNA viruses, arm-like segments located at the N or C termini have been suggested as mediators in the assembly of the capsid proteins. In many cases the arms of several subunits converge at a common point (the symmetry axis). Recent advances in studies of the hepatitis B virus (HBV) core protein attest the convergence of the segments preceding the protamine region, around the symmetry axis, where five or six HBc protein subunits converge. We report a mutation study of the region that we have suggested forms an armlike structure, which reveals that a single mutation, Pro-138 Gly, prevents the full-length HBV core protein self-assembling into particles.In many viruses, extended conformations frequently found at the N terminus of the capsid protein are supposed to play an important role in the assembly of the viral particles (Harrison, 1992). In simian virus 40, for example, the capsid contains 72 pentamers of the VP1 protein. The pentamers are linked by the interaction of the C-terminal arms of the VP1 protein with five or six neighbouring pentamers (Liddington et al., 1991). These interactions supplant the absence of complementary interfaces between pentamers.The human hepatitis B virus (HBV) has been shown to form particles of two different sizes, one major population of capsids containing 240 copies of HBc protein (T l 4 capsids, where T is the triangulation number) and a minor population of capsids containing 180 copies (T l 3 capsids) (Crowthers et al., 1994 ;Kenney et al., 1995 ;Zlotnick et al., 1996). In both cases, the capsids reveal tightly clustered dimers composed of a shell domain and a protruding spike. Two recent papers (Bo$ ttcher et al., 1997 ;Conway et al., 1997) have made an important contribution to the knowledge of the structure of the HBV capsid. It has been revealed that the previously reported

Enhanced stability of a chimeric hepatitis B core antigen virus-like-particle (HBcAg-VLP) by a C-terminal linker-hexahistidine-peptide

“…This rare sequence conservation indicates highly crucial residues. The cruciality has already been shown for the three C-terminal residues (gly111 to pro138), which are essential for folding or capsid formation [ 54 , 59 , 60 ]. The functions of his47 have not been studied systematically.…”

The morphogenic linker peptide of HBV capsid protein forms a mobile array on the interior surface

“…It has previously been reported that Cp138 is not assembly competent (Birnbaum and Nassal, 1990; Beames and Lanford, 1993; Metzger and Bringas, 1998), and we have found that Cp139 shares this property. Moreover, a monoclonal antibody that bound to Cp140 failed to react with Cp138 (Salfeld et al ., 1989), suggesting a different conformation.…”

Hepatitis B viral core proteins with an N-terminal extension can assemble into core-like particles but cannot be enveloped

“…The N-terminal portion (aa 1–150) of core protein is capable of self- assembling into nucleocapsids even in the absence of the C terminus (Birnbaum & Nassal, 1990 ; Nassal, 1992 ; Halton et al , 1992 ). In contrast, core mutants bearing a small insertion, substitution or deletion in the N-terminal domain of HBV core protein (Beames & Lanford, 1995 ; Metzger & Bringas, 1998 ; Konig et al , 1998 ) or woodchuck hepatitis virus (WHV) core protein (Yu et al , 1996 ) fail to form nucleocapsids. However, studies on duck HBV show that the core protein N-terminal additions have various effects on capsid formation depending on the nature of the extension peptides (von Weizsacker et al , 1996 ; Kock et al , 1998 ).…”