title: Deletion of xylR gene enhances expression of xylose isomerase in Streptomyces lividans TK24.
abstract: Glucose (xylose) isomerases from Streptomyces sp. have been used for the production of high fructose corn syrup for industrial purposes. An 11-kb DNA fragment containing the xyl gene cluster was isolated from Streptomyces lividans TK24 and its nucleotide sequences were analyzed. It was found that the xyl gene cluster contained a putative transcriptional repressor (xylR), xylulokinase (xylB), and xylose isomerase (xylA) genes. The transcriptional directions of the xylB and xylA genes were divergent, which is consistent to those found in other streptomycetes. A gene encoding XylR was located downstream of the xylB gene in the same direction, and its mutant strain produced xylose isomerase regardless of xylose in the media. The enzyme expression level in the mutant was 4.6 times higher than that in the parent strain under xylose-induced condition. Even in the absence of xylose, the mutant strain produce over 60% of enzyme compared with the xylose-induced condition. Gel mobility shift assay showed that XylR was able to bind to the putative xyl promoter, and its binding was inhibited by the addition of xylose in vitro. This result suggested that XylR acts as a repressor in the S. lividans xylose operon.
authors.affiliation: Department of Agricultural Chemistry, Kyungpook National University, Daegu 702-701, Korea.
authors.forename: Gun-Young
authors.initials: GY
authors.lastname: Heo
authors.forename: Won-Chan
authors.initials: WC
authors.lastname: Kim
authors.forename: Gil-Jae
authors.initials: GJ
authors.lastname: Joo
authors.forename: Yun-Young
authors.initials: YY
authors.lastname: Kwak
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Shin
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Roh
authors.forename: Heui-Dong
authors.initials: HD
authors.lastname: Park
authors.forename: In-Koo
authors.initials: IK
authors.lastname: Rhee
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D005810:Multigene Family; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017384:Sequence Deletion; D048170:Streptomyces lividans / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase