Structure of the hepatitis A virion: identification of potential surface-exposed regions

Abstract

Iodination of highly purified hepatitis A (HAV) virus results in the selective labeling of two viral polypeptides, which are identified as the the VP 1 and VP 2 capsid polypeptides. Based upon the kinetics of labeling, the exposed region of VP 1 appears to be more accessible to iodination, although the ultimate proportion of label present within VP 1 and VP 2 is approximately equal. By utilizing iodinated whole virions, isolated VP 1, VP 2, and the tryptic digest derived from VP 1 and VP 2, binding by heterologous anti-160 S antibody indicated that a significant portion of the antibodies was directed against an epitope on VP 2 that was not affected by denaturation. Identification of the regions exposed for iodination on these two polypeptides was accomplished by tryptic digestion of the isolated polypeptides followed by characterization of the iodinated tryptic peptide by gel filtration and reverse-phase chromatography. The results indicate that tyrosine 100 on VP 2 and a large tryptic peptide composed of amino acids 222 through 260 on VP 1 which contains four tyrosine residues are two regions that are surface-exposed on these molecules.

Protease digestion of hepatitis A virus: disparate effects on capsid proteins, antigenicity, and infectivity

“…Its position within VP3 aligns with residues forming an antigenic loop of VP3 in other picornaviruses (13). These findings are consistent with the hypothesis that Asp-70 may be located near the base of an antigenic loop, as Luo et al (10) suggested with a model of the HAV structure based on the crystallographically defined structure of type 14 rhinovirus. In such a position, substitution with other amino acids could significantly influence the conformation of the putative VP3 B-C loop, but the residue could remain protected from protease attack.…”

“…Moreover, high concentrations of protease, low concentrations of substrate, and prolonged incubation times such as were used in these experiments may alter the specificities of proteases (12). Nonetheless, Robertson et al (14) have suggested that Tyr-100 of VP2 is present on the surface of the virion and may be iodinated by surface-labeling procedures. Since chymotrypsin preferentially cleaves proteins following residues with large, aromatic side chains, Tyr-100 is a potential site for cleavage by chymotrypsin while the adjacent Arg-99 is a potential site for trypsin cleavage.…”

A new continuous epitope of hepatitis A virus

“…To resolve this question, it has been suggested that mutations in one residue could affect the immunoglobulin binding to the other, although they are very ditant from one another [Nainan et al, 1992]. However, the very exposed VP2(96-107) sequence [Luo et al, 1988;Robertson et al, 1989] failed to induce an immune response comparable to that of VP3(110-121). In any case, all these paradigms cannot be answered before the resolution of the actual HAV capsid structure.…”

“…In the present study, three synthetic peptides were selected for the search of antigenic sites of HAV: VP1(11-25) (TVSTEQNVPDPQVGI) [Emini et al, 1985], the surface-exposed VP2(96-107) (GLLRYHT-YARFG) [Robertson et al, 1989], and the hydrophilic VP3(110-121) (FWRGDLVFDFQV) [Wheeler et al, 1986], which includes the tetrapeptide RGDL and is also included in neutralisation site A of foot-andmouth-disease virus [Verdaguer et al, 1995]. Fig.…”

Growth of Hepatitis A Virus in a Mouse Liver Cell Line

“…Interestingly, N1237D is adjacent to Q1232, a residue that is within the major antigenic site of HAV (26). In addition, Y1236 has been shown to be accessible to iodination in highly purified virions (30), which also suggests that this residue is exposed at the virion surface. Therefore, it is possible that amino acid residues 237 of VP1 and 132 of VP2 are indeed located at the surface of the HAV particle and that mutations N1237D and D2132G allowed the interaction of HAV-MMH with a mouse receptor that medi- ated cell entry.…”