Molecular cloning and expression in Streptomyces lividans of a proteinous alpha-amylase inhibitor (HaimII) gene from Streptomyces griseosporeus.

The gene encoding a proteinous alpha-amylase inhibitor (HaimII) of Streptomyces griseosporeus YM-25 has been cloned in Escherichia coli K12 using a deoxyinosine-containing synthetic oligonucleotide as the probe. A 1.6 kilobases BamHI fragment was confirmed to hybridize with the probe and subcloned in an E. coli-S. lividans shuttle vector. The plasmid clone was transferred into S. lividans by transformation. An appreciable amount of alpha-amylase inhibitor activity was found in the culture medium of S. lividans harboring the plasmid. As the specificity was indistinguishable from that of HaimII produced by the original S. griseosporeus strain, we concluded that the HaimII protein was synthesized in S. lividans and excreted into the medium.