Disruption of sblA in Streptomyces lividans permits expression of a heterologous α-amylase gene in the presence of glucose

In a transposition mutant of Streptomyces lividans TK24, the usually glucose-repressible expression of a heterologous α-amylase gene (aml) became resistant to glucose repression. The transposon had inserted into an ORF called sblA which encodes a 274 aa product sharing significant sequence similarities with various phosphatases that act on small phosphorylated substrates. sblA was transcribed as a monocistronic mRNA and its transcription was enhanced at the transition phase. Because its transcriptional and putative translational start points coincide, sblA is likely to be translated in the absence of a conventional RBS. The sblA-disrupted mutant is characterized by early growth arrest in glucose-grown cultures and by partial relief of glucose repression of aml expression.