Abstract:
:Cells of Escherichia coli take up vitamin B(12) (cyano-cobalamin [CN-Cbl]) and iron chelates by use of sequential active transport processes. Transport of CN-Cbl across the outer membrane and its accumulation in the periplasm is mediated by the TonB-dependent transporter BtuB. Transport across the cytoplasmic membrane (CM) requires the BtuC and BtuD proteins, which are most related in sequence to the transmembrane and ATP-binding cassette proteins of periplasmic permeases for iron-siderophore transport. Unlike the genetic organization of most periplasmic permeases, a candidate gene for a periplasmic Cbl-binding protein is not linked to the btuCED operon. The open reading frame termed yadT in the E. coli genomic sequence is related in sequence to the periplasmic binding proteins for iron-siderophore complexes and was previously implicated in CN-Cbl uptake in Salmonella. The E. coli yadT product, renamed BtuF, is shown here to participate in CN-Cbl uptake. BtuF protein, expressed with a C-terminal His(6) tag, was shown to be translocated to the periplasm concomitant with removal of a signal sequence. CN-Cbl-binding assays using radiolabeled substrate or isothermal titration calorimetry showed that purified BtuF binds CN-Cbl with a binding constant of around 15 nM. A null mutation in btuF, but not in the flanking genes pfs and yadS, strongly decreased CN-Cbl utilization and transport into the cytoplasm. The growth response to CN-Cbl of the btuF mutant was much stronger than the slight impairment previously described for btuC, btuD, or btuF mutants. Hence, null mutations in btuC and btuD were constructed and revealed that the btuC mutant had a strong impairment similar to that of the btuF mutant, whereas the btuD defect was less pronounced. All mutants with defective transport across the CM gave rise to frequent suppressor variants which were able to respond at lower levels of CN-Cbl but were still defective in transport across the CM. These results finally establish the identity of the periplasmic binding protein for Cbl uptake, which is one of few cases where the components of a periplasmic permease are genetically separated.
journal_name
J Bacterioljournal_title
Journal of bacteriologyauthors
Cadieux N,Bradbeer C,Reeger-Schneider E,Köster W,Mohanty AK,Wiener MC,Kadner RJdoi
10.1128/jb.184.3.706-717.2002keywords:
subject
Has Abstractpub_date
2002-02-01 00:00:00pages
706-17issue
3eissn
0021-9193issn
1098-5530journal_volume
184pub_type
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journal_title:Journal of bacteriology
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doi:10.1128/jb.172.3.1368-1373.1990
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abstract::Utilizing a homologous gene replacement in order to retain the native promoter and 5' and 3' untranslated messenger regions (and thereby ensure physiological validity), we have shown that deletion of the N-terminal 389 amino acids of the transcriptional activator AREA does not result in nitrogen metabolite derepressio...
journal_title:Journal of bacteriology
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doi:10.1128/JB.180.21.5762-5764.1998
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journal_title:Journal of bacteriology
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doi:10.1128/JB.98.3.1044-1055.1969
更新日期:1969-06-01 00:00:00
abstract::Cell suspensions of Bacteroides fragilis were allowed to ferment glucose and lactate labeled with (14)C in different positions. The fermentation products, propionate and acetate, were isolated, and the distribution of radioactivity was determined. An analysis of key enzymes of possible pathways was also made. The resu...
journal_title:Journal of bacteriology
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journal_title:Journal of bacteriology
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doi:10.1128/JB.88.1.93-95.1964
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.96.4.1029-1036.1968
更新日期:1968-10-01 00:00:00
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doi:10.1128/jb.170.2.865-871.1988
更新日期:1988-02-01 00:00:00
abstract::Mutants of Agrobacterium tumefaciens requiring methionine for growth on a solid basal medium were induced by the use of N-methyl-N'-nitro-N-nitrosoguanidine. In addition to the difference of mutant strains, the extent of methionine dependency differed in a liquid basal medium and in the presence of aspartate or fumara...
journal_title:Journal of bacteriology
pub_type: 杂志文章
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更新日期:1968-06-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.172.10.5637-5642.1990
更新日期:1990-10-01 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:2008-06-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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pub_type: 杂志文章
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更新日期:2006-12-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.168.3.1451-1456.1986
更新日期:1986-12-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.133.2.492-498.1978
更新日期:1978-02-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.175.7.1981-1987.1993
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
doi:10.1128/JB.132.2.718-722.1977
更新日期:1977-11-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.96.6.2018-2024.1968
更新日期:1968-12-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.179.1.280-283.1997
更新日期:1997-01-01 00:00:00
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pub_type: 杂志文章
doi:10.1128/JB.88.4.1145-1150.1964
更新日期:1964-10-01 00:00:00
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更新日期:1983-11-01 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:1995-04-01 00:00:00
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更新日期:1971-10-01 00:00:00
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pub_type: 杂志文章
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更新日期:1969-05-01 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:2008-02-01 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:1993-06-01 00:00:00
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pub_type: 杂志文章
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更新日期:1978-10-01 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:1975-10-01 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:2005-10-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.165.1.334-335.1986
更新日期:1986-01-01 00:00:00