| abstract |
A polynucleotide molecule comprising a nucleotide sequence that is the same as the Streptomyces avermitilis aveC allele, the S. avermitilis AveC gene product-encoding sequence of the plasmid pSE186 according to ATCC 209604 or the nucleotide sequence of the aveC ORF of S. avermitilis according to SEQ ID NO: 1, or a degenerate variant thereof, but which nucleotide sequence further comprises one or more amino acid substitutions at one or more amino acid residues corresponding to amino acid positions 38, 48, 89, 99, 111, 136 , 138, 154, 179, 228, 238, 289, or 298 of SEQ ID NO: 2, cells of S. avermitilis strain ATCC 53692 in which the wild-type aveC has been inactivated and that expresses the polynucleotide molecule comprising cyclohexyl B2: cyclohexyl B1 avermectins that is reduced from the ratio produced by cells of S. avermitilis strain ATCC 53692 le. A recombinant vector and host cell, and a method of making a strain of S. avermitilis, including mutating the aveC allele, and a mutated cell of this strain and a process for producing said avermectins and a final composition. |