Kluyveromyces lactis killer system: identification of a new gene encoded by pGKL2.

The cytoplasmic linear plasmid pGKL2 of the yeast Kluyveromyces lactis was reported to harbour ten open reading frames (ORF1-ORF10). By re-examining the sequence, we identified an additional ORF encoding a polypeptide of 70 amino acids; and a homologous ORF with 70% similarity was also identified on plasmid pSKL of Saccharomyces kluyveri. As for pGKL2, the newly detected ORF11 is located at the same position with the same direction. ORF11 transcripts of pGKL2 were verified by reverse transcriptase-polymerase chain reaction; and the corresponding promoter activity was proven by expression of a reporter gene driven by the ORF11 upstream conserved sequence, indicating that ORF11 constitutes a functional gene.