Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2002-1-8
pubmed:abstractText
We have previously shown that the activity of NhaA is regulated by pH and found mutations that affect dramatically the pH dependence of the rate but not the K(m) (for Na(+) and Li(+)) of NhaA. In the present work, we found that helix IV is involved both in ion translocation as well as in pH regulation of NhaA. Two novel types of NhaA mutants were found clustered in trans membrane segment (TMS) IV: One type (D133C, T132C, and P129L) affects the apparent K(m) of NhaA to the cations with no significant effect on the pH profile of the antiporter; no shift of the pH profile was found when the activity of these mutants was measured at saturating Na(+) concentration. In contrast, the other type of mutations (A127V and A127T) was found to affect both the K(m) and the pH dependence of the rate of NhaA whether tested at saturating Na(+) concentration or not. These results imply that residues involved in the ion translocation of NhaA may (A127) or may not (D133, T132, and P129) overlap with those affecting the pH response of the antiporter. All mutants cluster in the N-terminal half of the putative alpha-helix IV, one type on one face, the other on the opposite. Cys accessibility test demonstrated that although D133C is located in the middle of TMS IV, it is inhibited by N-ethylmaleimide and is exposed to the cytoplasm.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
41
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
609-17
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:11781101-Amino Acid Sequence, pubmed-meshheading:11781101-Cell Membrane, pubmed-meshheading:11781101-Cysteine, pubmed-meshheading:11781101-Cytoplasm, pubmed-meshheading:11781101-Dose-Response Relationship, Drug, pubmed-meshheading:11781101-Escherichia coli, pubmed-meshheading:11781101-Escherichia coli Proteins, pubmed-meshheading:11781101-Ethylmaleimide, pubmed-meshheading:11781101-Hydrogen-Ion Concentration, pubmed-meshheading:11781101-Ions, pubmed-meshheading:11781101-Kinetics, pubmed-meshheading:11781101-Molecular Sequence Data, pubmed-meshheading:11781101-Mutagenesis, Site-Directed, pubmed-meshheading:11781101-Mutation, pubmed-meshheading:11781101-Phenotype, pubmed-meshheading:11781101-Plasmids, pubmed-meshheading:11781101-Protein Binding, pubmed-meshheading:11781101-Protein Structure, Secondary, pubmed-meshheading:11781101-Protein Structure, Tertiary, pubmed-meshheading:11781101-Protein Transport, pubmed-meshheading:11781101-Sequence Homology, Amino Acid, pubmed-meshheading:11781101-Sodium, pubmed-meshheading:11781101-Sodium-Hydrogen Antiporter, pubmed-meshheading:11781101-Time Factors
pubmed:year
2002
pubmed:articleTitle
Trans membrane domain IV is involved in ion transport activity and pH regulation of the NhaA-Na(+)/H(+) antiporter of Escherichia coli.
pubmed:affiliation
Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't