Functional regulation of PVBV Nuclear Inclusion protein-a protease activity upon interaction with Viral Protein genome-linked and phosphorylation

Abstract

Regulation of NIa-Pro is crucial for polyprotein processing and hence, for successful infection of potyviruses. We have examined two novel mechanisms that could regulate NIa-Pro activity. Firstly, the influence of VPg domain on the proteolytic activity of NIa-Pro was investigated. It was shown that the turnover number of the protease increases when these two domains interact (cis: two-fold; trans: seven-fold) with each other. Secondly, the protease activity of NIa-Pro could also be modulated by phosphorylation at Ser129. A mutation of this residue either to aspartate (phosphorylation-mimic) or alanine (phosphorylation-deficient) drastically reduces the protease activity. Based on these observations and molecular modeling studies, we propose that interaction with VPg as well as phosphorylation of Ser129 could relay a signal through Trp143 present at the protein surface to the active site pocket by subtle conformational changes, thus modulating protease activity of NIa-Pro.

The Hypervariable Amino-Terminus of P1 Protease Modulates Potyviral Replication and Host Defense Responses

“…In silico analysis showed that the limited primary sequence conservation of the P1 N-terminal region is associated with residues predicted to be part of intrinsically disordered loops. The relevance of unfolded regions in the proteolytic maturation of viral polyproteins has been shown [6], [7], and flexible loops in peptidase precursors act in many cases as protease activation switches [39]. Previous results and those reported here show successful self-cleavage activity of potyviral P1 after in vitro translation only in the WGE system, but not in RRL.…”

“…For instance, it is not uncommon that the same polyprotein is hydrolyzed by several endopeptidases; cleavage kinetics are thus linked to enzyme processivity and, in trans -acting proteases, to the different affinity with the specific cleavage sites [3], [4]. Activation of viral proteases might depend on the availability of defined cell- or pathogen-encoded cofactors [5]–[7] and structural rearrangements that modulate substrate accessibility, as shown for the hepatitis C virus NS3 protease domain [8]. Zymogen activation and allostery are key regulatory mechanisms of trypsin-like proteases [9], a group of enzymes that is widespread in positive strand RNA viruses [10] and that includes P1 proteins of potyviruses [11].…”

Sharka: The Past, The Present and The Future

“…The NIa-Pro is a sequence-specific proteinase required for processing of viral polyprotein in the cytoplasm. This fact has been demonstrated in many potyviruses, such as pepper vein banding virus (PVBV), and is generally relevant for all known potyviruses [76]. Its accumulation in nuclei of infected cells manifested as a formation of “inclusion bodies” and has been demonstrated in some papers, for example see work of Anindya et al [71] or Restrepo et al [77].…”

Host Factors in the Infection Cycle of Bamboo mosaic virus

“…Post-translational modification, including ubiquitination, sumoylation, glycosylation, and phosphorylation of viral proteins, were issued as parts of an important process in modulating the structures and functions of viral proteins (Barajas and Nagy, 2010; Alcaide-Loridan and Jupin, 2012; Mathur et al, 2012; Perez Jde et al, 2013; Samuilova et al, 2013; Xiong and Wang, 2013). Maintaining the protein structural integrity, including those modifications of MP and CP, is critical for virus movement.…”