Intrinsic disorder in the open reading frame 2 of hepatitis E virus: a protein with multiple functions beyond viral capsid
Background
Hepatitis E virus(HEV) is the cause of a liver disease hepatitis E. The translation product of HEVORF2has recently been demonstrated as a protein involved in multiple functions besides performing its major role of aviral capsid. As intrinsically disordered regions (IDRs) are linked to various essential roles in the virus’slife cycle, we analyzed the disorder pattern distribution of the retrievedORF2protein sequencesby employing different online predictors. Our findings might provide some clues on the disorder-based functions of ORF2 protein that possibly help us in understanding its behavior other than as a HEVcapsid protein.
Results
The modeled three dimensional (3D) structures of ORF2 showed the predominance of random coils or unstructured regions in addition to majorsecondary structurecomponents (alpha helix and beta strand). After initial scrutinization, the predictors VLXT and VSL2 predicted ORF2 as a highly disordered protein while the predictors VL3 and DISOPRED3 predicted ORF2 as a moderately disordered protein, thus categorizing HEV-ORF2 into IDP (intrinsically disordered protein) or IDPR (intrinsically disordered protein region) respectively. Thus, our initial predicted disorderness in ORF2 protein 3D structures was in excellent agreement with their predicted disorder distribution patterns (evaluated through different predictors). The abundance ofMoRFs(disorder-basedprotein bindingsites) in ORF2 was observed that signified their interaction with binding partners which might further assist in viral infection. As IDPs/IDPRs are targets of regulation, we carried out the phosphorylation analysis to reveal the presence of post-translationally modified sites. Prevalence of several disordered-based phosphorylation sites further signified the involvement of ORF2 in diverse and significantbiological processes. Furthermore, ORF2 structure-associated functions revealed its involvement in several crucial functions andbiological processeslike binding and catalytic activities.
Conclusions
The results predicted ORF2 as a protein with multiple functions besides its role as acapsid protein. Moreover, the occurrence of IDPR/IDP in ORF2 protein suggests that its disordered region might serve as novel drug targets via functioning as potential interacting domains. Our data collectively might provide significant implication inHEV vaccinesearch as disorderness inviral proteinsis related to mechanisms involved in immune evasion.