Differential proteolytic activities of precursor and mature forms of the 24K proteinase of grapevine fanleaf nepovirus.
The presence of a genome-linked protein (VPg) at the RNA 5'-end of the genome is a characteristic of different groups of animal and plant positive-sense single-stranded RNA viruses. These viruses express their structural and functional proteins from polyproteins that are sequentially processed by at least one viral proteinase. The grapevine fanleaf nepovirus 24K chymotrypsin-like cysteine proteinase, located between the VPg and the RNA polymerase in the RNA-1 encoded polyprotein P1, is active in its free form and in various precursors forms. The VPg proteinase precursor (VPg-Pro) constitutes a stable protein and its maturation in the reticulocyte lysate system occurs at a very low rate. Differences on cleavage activity were observed between the proteinase and its VPg-Pro precursor forms, depending upon the cleavage site considered. The proteinase alone has a greater cleavage efficiency than VPg-Pro at the Arg605/Gly606 and Cys257/Ala258 sites of polyprotein P2. On the other hand, the presumed Cys415/Ala416 site, present at the amino terminus of polyprotein P1, was preferentially cleaved by the VPg-Pro precursor. During their in vitro maturation, proteins containing the VPg proteinase-polymerase coding region or the proteinase-polymerase region were similar in their ability to cleave in cis between the proteinase and the RNA polymerase.
Margis
R
R
Institut de Biologie Moléculaire des Plantes du CNRS et Université Louis Pasteur, Strasbourg, France.
Viry
M
M
Pinck
M
M
Bardonnet
N
N
Pinck
L
L
D001483:Base Sequence; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D017860:Nepovirus / Q000201:enzymology* / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*
D011498:Protein Precursors; D014758:Viral Core Proteins; D012321:DNA-Directed RNA Polymerases; D003546:Cysteine Endopeptidases; C071903:GFLV VP7 proteinase