The complete nucleotide sequence of RNA1 of barley mild mosaic virus (ASL1) and attempts at bacterial expression of the P3 protein

The complete nucleotide sequence of RNA1 of an Aschersleben isolate of barl ey mild mosaic virus (BaMMV) was determined. It consists of 7263 nucleotide s (nt) excluding the 3' poly (A) tail. The 5' and 3' nontranslated regions (NTR) are 148 and 338 nt in length, respectively, and flank a single large open reading frame coding for a precursor polypeptide with a calculated mol ecular mass of 256 kDa. Sequence comparison revealed a 96% amino acid (aa) identity to RNA1 translation products of Japanese and French BaMMV isolates . Conserved nucleotide motifs in the 3' sense and 5' complementary sense NT R of the two genomic RNAs were identified that may represent the polymerase recognition sites. A range of constructs containing various parts of the c oding region of the P3 nonstructural protein was prepared for expression in Escherichia coli. A short stretch of 35 aa in the C-proximal region of P3 appeared to be highly toxic to the bacterium.