Novel NTP binding property of rice dwarf phytoreovirus minor core protein P5.
Rice dwarf phytoreovirus (RDV) mRNA synthesized from purified virion has a cap structure, m7GpppAm-, which suggests the presence of guanylyltransferase activity in the virion. We attempted to identify the enzyme involved in the cap formation by using a nucleoside triphosphate binding assay. Incubation of virion with [alpha-32P]GTP resulted in labeling of an 89-kDa protein that had not previously been identified in purified virus preparations. Interestingly this protein also covalently bound UTP and ATP, which is not a property of the known guanylytransferases. RDV particles catalyzed GTP-PPi, dGTP-PPi, ATP-PPi, and UTP-PPi exchange reactions. In SDS-polyacrylamide gel electrophoresis, the 89-kDa protein comigrated with the S5-coded protein, P5, which had been expressed by a baculovirus vector. Moreover, the labeled 89-kDa protein was precipitated by an antiserum against this recombinant RDV P5. Careful reinvestigation of purified virus particles by SDS-polyacrylamide gel electrophoresis and Western blotting analyses showed that they contained a small amount of P5 (<0.5% of the total protein) within the core. These results may suggest that the minor core protein of RDV, which is coded by S5, is a candidate guanylyltransferase, although the biological significance of its ATP and UTP binding activities remains largely unknown.
Suzuki
N
N
Laboratory of Plant Genetic Engineering, Akita Prefectural College of Agriculture, Japan.
Kusano
T
T
Matsuura
Y
Y
Omura
T
T
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D006160:Guanosine Triphosphate / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000378:metabolism; D012275:Oryza / Q000821:virology; D010942:Plant Viruses / Q000737:chemistry / Q000378:metabolism*; D012087:Reoviridae / Q000737:chemistry / Q000378:metabolism*; D018411:Spodoptera / Q000166:cytology; D014544:Uridine Triphosphate / Q000378:metabolism; D014758:Viral Core Proteins / Q000378:metabolism*
D009711:Nucleotides; D014758:Viral Core Proteins; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D009713:Nucleotidyltransferases; C020842:guanylyltransferase; D014544:Uridine Triphosphate