Linked Life Data

17411076

Source:http://linkedlifedata.com/resource/pubmed/id/17411076

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
17
pubmed:dateCreated
2007-4-24
pubmed:abstractText
NikA is a periplasmic binding protein involved in nickel uptake in Escherichia coli. NikA was identified as a heme-binding protein in the periplasm of anaerobically grown cells overexpressing CydDC, an ABC transporter that exports reductant to the periplasm. CydDC-overexpressing cells accumulate a heme biosynthesis-derived pigment, P-574. For further biochemical and spectroscopic analysis, unliganded NikA was overexpressed and purified. NikA was found to comigrate with both hemin and protoporphyrin IX during gel filtration. Furthermore, tryptophan fluorescence quenching titrations demonstrated that both hemin and protoporphyrin IX bind to NikA with similar affinity. The binding affinity of NikA for these pigments (Kd approximately 0.5 microM) was unaltered in the presence and absence of saturating concentrations of nickel, suggesting that these tetrapyrroles bind to NikA in a manner independent of nickel. To test the hypothesis that NikA is required for periplasmic heme protein assembly, the effects of a nikA mutation (nikA::Tn5, Km(R) insertion) on accumulation of P-574 by CydDC-overexpressing cells was assessed. This mutation significantly lowered P-574 levels, implying that NikA may be involved in P-574 production. Thus, in the reducing environment of the periplasm, NikA may serve as a heme chaperone as well as a periplasmic nickel-binding protein. The docking of heme onto NikA was modeled using the published crystal structure; many of the predicted complexes exhibit a heme-binding cleft remote from the nickel-binding site, which is consistent with the independent binding of nickel and heme. This work has implications for the incorporation of heme into b- and c-type cytochromes.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
46
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5030-7
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
NikA binds heme: a new role for an Escherichia coli periplasmic nickel-binding protein.
pubmed:affiliation
Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't