We have isolated and sequenced a gene (
amy) coding for α-amylase [EC. 3.2.1.1] from the
Streptomyces hygroscopicus genome. Subcloning experiments indicated that
amy could be expressed from the
lac promoter in
E. coli or its own promoter in
S. lividans. The
amy nucleotide sequence indicated that it coded for a protein of 52 kilodaltons (478 amino acids). The conserved amino acid sequences of other α-amylase were found in three separate regions of the
S. hygroscopicus α-amylase. The 30-residue leader sequence showed similarities to those found in other prokaryotes. The DNA sequence 5′ to the
amy structural gene contained a sequence complementary to the 3′-terminal sequence of 16S rRNA of
S. lividans. The transcriptional start points of
amy were determined, but the promoter of
amy was not similar to the consensus sequence found in other prokaryotes. The recombinant strain,
S. hygroscopicus containing
amy on a high copy plasmid, produced α-amylase 4 times excess than the host strain.
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