AFRICAN SWINE FEVER VIRUS TRANS-PRENYLTRANSFERASE

The present study describes the characterization of an African swine f ever virus gene homologous to prenyltransferases. The gene, designated B318L, is located within the EcoRI B fragment in the central region o f the virus genome, and encodes a polypeptide with a predicted molecul ar weight of 35,904. The protein is characterized by the presence of a putative hydrophobic transmembrane domain at the amino end. The gene is expressed at the late stage of virus infection, and transcription i s initiated at positions -118, -119, -120, and -122 relative to the fi rst nucleotide of the translation start codon. Protein B318L presents a colinear arrangement of the four highly conserved regions and the tw o aspartate-rich motifs characteristic of geranylgeranyl diphosphate s ynthases, farnesyl diphosphate synthases, and other prenyltransferases . Throughout these regions, the percentages of identity between protei n B318L and various prenyltransferases range from 28.6 to 48.7%. The g ene was cloned in vector pTrxFus without the amino-terminal hydrophobi c region and expressed in Escherichia coli. The recombinant protein, p urified essentially to homogeneity by affinity chromatography, catalyz es the sequential condensation of isopentenyl diphosphate with differe nt allylic diphosphates, farnesyl diphosphate being the best allylic s ubstrate of the reaction. All-trans-polyprenyl diphosphates containing 3-13 isoprene units are synthesized, which identifies the B318L prote in as a trans-prenyltransferase.