The transmembrane domain and the proton channel in proton-pumping transhydrogenases
| Autor: | Johan Meuller, Jan Rydström, Tania Bizouarn, Magnus A B Axelsson |
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| Rok vydání: | 2000 |
| Předmět: |
Models
Molecular Stereochemistry Molecular Sequence Data Biophysics Protonation Nicotinamide nucleotide Nicotinamide adenine dinucleotide Biochemistry Transhydrogenase chemistry.chemical_compound Escherichia coli NADP Transhydrogenases Nucleotide Amino Acid Sequence chemistry.chemical_classification Helix bundle Binding Sites Nicotinamide adenine dinucleotide phosphate Mutagenesis Wild type Cell Biology Proton Pumps Proton pump Transmembrane domain chemistry Membrane protein NAD+ kinase NADP |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1459:284-290 |
| ISSN: | 0005-2728 |
| Popis: | Proton-pumping nicotinamide nucleotide transhydrogenases are composed of three main domains, the NAD(H)-binding and NADP(H)-binding hydrophilic domains I (dI) and III (dIII), respectively, and the hydrophobic domain II (dII) containing the assumed proton channel. dII in the Escherichia coli enzyme has recently been characterised with regard to topology and a packing model of the helix bundle in dII is proposed. Extensive mutagenesis of conserved charged residues of this domain showed that important residues are betaHis91 and betaAsn222. The pH dependence of betaH91D, as well as betaH91C (unpublished), when compared to that of wild type shows that reduction of 3-acetylpyridine-NAD(+) by NADPH, i.e., the reverse reaction, is optimal at a pH essentially coinciding with the pK(a) of the residue in the beta91 position. It is therefore concluded that the wild-type transhydrogenase is regulated by the degree of protonation of betaHis91. The mechanisms of the interactions between dI+dIII and dII are suggested to involve pronounced conformational changes in a 'hinge' region around betaR265. |
| Databáze: | OpenAIRE |
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