Cloning of a Gene Cluster for Dextrin Utilization from Thermoactinomyces vulgaris R-47 and Characterization of the Cyclodextrin-binding Protein.

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To investigate the physiological role of an α-amylase, TVA II from Thermoactinomyces vulgaris R-47, which hydrolyze cyclodextrins and pullulan, a region located upstream of the TVA II gene was cloned and sequenced. Five open reading frames, designated as ORF-1 to -5, were found in a fragment of about 5 kbp. Three of these genes, ORF-1, -2 and -3, were homologous to the genes which encode proteins related to the sugar metabolic systems, such a maltose system of Esch erichia coli and cyclodextrin metabolic system of Klebsiella oxytoca. An expression vector for the ORF-3 protein, which was similar to maltose-binding protein from E. coli (MalE) and a cyclodextrinbinding protein from K. oxytoca (CymE), was constructed, and the expressed ORF-3 protein was purified. The ORF-3 protein was a cyclodextrin-binding protein because of having a higher binding ability for cyclodextrins than for maltose.