Abstract:
:In streptomycete anthracycline biosynthetic gene clusters, small open reading frames are located just upstream of minimal polyketide synthase genes. aknX is such a gene found in the aklavinone-aclacinomycin biosynthetic gene cluster of Streptomyces galilaeus. In order to identify its function, the aknX gene was expressed in Escherichia coli. The cell extract prepared from E. coli cells overexpressing AknX protein exhibited anthrone oxygenase activity, which converted emodinanthrone to anthraquinone emodin. This indicates that AknX and related gene products such as DnrG and SnoaB are involved in the formation of aklanonic acid from its anthrone precursor, as suggested by their homology with TcmH and ActVA6. The AknX protein fused with a His(6) tag was efficiently purified to homogeneity by Ni(2+) affinity and anion-exchange column chromatography. The native molecular mass of AknX was estimated to be 42 kDa by gel filtration. Thus, native AknX is considered to have a homotrimeric subunit structure. AknX, like TcmH and ActVA6, possesses no apparent prosthetic group for oxygen activation. Site-directed mutagenesis was carried out to identify the key amino acid residue(s) involved in the oxygenation reaction. Of seven AknX mutants expressed, the W67F mutant showed significantly reduced oxygenase activity, suggesting the important role of the W67 residue in the AknX reaction. A possible mechanism for the reaction via peroxy anion intermediate is proposed.
journal_name
J Bacterioljournal_title
Journal of bacteriologyauthors
Chung JY,Fujii I,Harada S,Sankawa U,Ebizuka Ydoi
10.1128/jb.184.22.6115-6122.2002keywords:
subject
Has Abstractpub_date
2002-11-01 00:00:00pages
6115-22issue
22eissn
0021-9193issn
1098-5530journal_volume
184pub_type
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journal_title:Journal of bacteriology
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journal_title:Journal of bacteriology
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.121.1.197-203.1975
更新日期:1975-01-01 00:00:00
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更新日期:2004-09-01 00:00:00
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pub_type: 杂志文章
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更新日期:1998-02-01 00:00:00
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pub_type: 杂志文章
doi:10.1128/JB.120.1.101-105.1974
更新日期:1974-10-01 00:00:00
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更新日期:1966-02-01 00:00:00
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pub_type: 杂志文章
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更新日期:1984-03-01 00:00:00
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pub_type: 杂志文章
doi:10.1128/JB.113.2.1034-1045.1973
更新日期:1973-02-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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更新日期:2007-02-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.175.23.7515-7522.1993
更新日期:1993-12-01 00:00:00
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pub_type: 杂志文章
doi:10.1128/jb.175.7.1871-1878.1993
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pub_type: 杂志文章
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更新日期:1986-07-01 00:00:00
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journal_title:Journal of bacteriology
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更新日期:1989-10-01 00:00:00
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journal_title:Journal of bacteriology
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更新日期:2001-01-01 00:00:00
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更新日期:1986-02-01 00:00:00
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pub_type: 杂志文章
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更新日期:1967-03-01 00:00:00
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更新日期:2008-06-01 00:00:00
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pub_type: 杂志文章
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更新日期:2004-06-01 00:00:00
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更新日期:1993-04-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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更新日期:1961-10-01 00:00:00
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pub_type: 杂志文章
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更新日期:1989-04-01 00:00:00
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更新日期:2011-06-01 00:00:00