Linked Life Data

15470119

Source:http://linkedlifedata.com/resource/pubmed/id/15470119

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
Pt 10
pubmed:dateCreated
2004-10-7
pubmed:abstractText
Cytochrome bd is a respiratory quinol oxidase in Escherichia coli. Besides the structural genes (cydA and cydB) encoding the oxidase complex, the cydD and cydC genes, encoding an ABC-type transporter, are required for assembly of this oxidase. Recently, cysteine has been identified as a substrate (allocrite) that is transported from the cytoplasm by CydDC, but the mechanism of cysteine export to the periplasm and its role there remain unknown. To initiate an understanding of structure-function relationships in CydDC, its membrane topography was analysed by generating protein fusions between random and selected residues in the two polypeptides with both alkaline phosphatase and beta-galactosidase. CydD and CydC are experimentally shown each to have six transmembrane segments, two major cytoplasmic loops and three minor periplasmic loops; both termini of each protein face the cytoplasm. The cydD1 allele is shown to have two point mutations (G319D, G429E) within the ATP-binding domain of CydD; either mutation alone is sufficient to cause loss or severe reduction of cytochrome bd assembly. A comparative sequence analysis prompted the targeting of residues in CydD for site-directed mutational analysis, which identified (i) the 'start' methionine residue, (ii) essential residues in the ATP-binding site (Walker sequence A) and (iii) a duplicated positively charged heptameric motif, R-G/T-L/M-X-T/V-L-R, in CydD cytoplasmic loop II. The replacement of arginines in these motifs with glycines resulted in Cyd- phenotypes; however, activity could be restored at these positions by replacing the glycine with lysine or histidine and hence returning the positive charge. The conservation of these charges in CydD-like proteins indicates functional importance. Evolutionary aspects of bacterial cyd genes are discussed.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
1350-0872
pubmed:author
pubmed:issnType
Print
pubmed:volume
150
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3415-27
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2004
pubmed:articleTitle
Membrane topology and mutational analysis of Escherichia coli CydDC, an ABC-type cysteine exporter required for cytochrome assembly.
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