Potyvirus Protein Analysis

Function of potyvirus proteins
The Potyviruses genome contains one open reading frame (ORF) which is translated as a large polyprotein (between 340k and 368k), that is cleaved into 10 functional proteins (Riechmann et al., 1992) such as: Protein P1, HC-Pro, P3 protein, CI, NIa , NIb, 6K1, 6K2, VPg. The potyviral P1 protein is a serine protease that cleaves at its own C-terminus (Verchot et al., 1991). This is the most divergent potyviral protein in size (30-63 kDa) and sequence except protease domain which is placed at C-terminal region (Yoshida et al.,2012Adams et al., 2005; Urcuqui-Inchimaet al., 2001). Protease domain is well conserved and catalytic triad H-(X7-11)-D-(X30-36)-S has been identified which is responsible for self-cleavage. …show more content…
The name of the protein derives from its first discovered function Helper Component (HC) for aphid transmission (Grovier et al.,1977). HC-Pro is cysteine protease that self- cleaves at C-terminus. Three structural domain can be distinguished in the HCPro protein: the N- and C- terminal regions, of approximately 100 amino acids and the central domain of approximately 250 amino acids (Plission et al., 2003). The C-terminal domain is responsible for the proteolytic activity of the protein and involved in multi functions (Soitamo et al., 2011), required viral acquisition by the vector, systemic and cell-to-cell movement and suppression of post transcriptional gene silencing (PTGS). The P3 protein is now one of the least well characterised Potyvirus proteins and a review about its functions is made by Urcuqui-Inchima et al. (2001). However, P3 has been shown to have a role in pathogenicity through interaction with other viral proteins; for instance, the C-terminal region of the P3-6K1 complex carries a pathogenicity determinant in PPV (Saenz et al., 2000). Similarly, Suehiro et al. (2004) showed that TuMV contained an important determinant in the P3 C-terminal region, which conferred the ability of virus to infect different