التفاصيل البيبلوغرافية
| العنوان: |
Importance for absorption of Na+ from freshwater of lysine, valine and serine substitutions in the alpha1a-isoform of Na,K-ATPase in the gills of rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). |
| المؤلفون: |
Jorgensen, Peter Leth |
| المصدر: |
Journal of Membrane Biology; May2008, Vol. 223 Issue 1, p37-47, 11p, 4 Diagrams, 3 Charts, 2 Graphs |
| مصطلحات موضوعية: |
RAINBOW trout, GILLS, ADENOSINE triphosphatase, ACCLIMATIZATION, MUTAGENESIS, FISH metabolism, POTASSIUM metabolism, LYSINE metabolism, SERINE metabolism, VALINE metabolism, AMINO acids, ANIMAL experimentation, COMPARATIVE studies, DOCUMENTATION, FISHES, ISOENZYMES, LYSINE, MATHEMATICAL models, RESEARCH methodology, MEDICAL cooperation, PHOSPHORYLATION, PROTEINS, RESEARCH, SODIUM, VALINE, WATER, SERINE, THEORY, EVALUATION research |
| مستخلص: |
In the gills of rainbow trout and Atlantic salmon, the alpha1a- and alpha1b-isoforms of Na,K-ATPase are expressed reciprocally during salt acclimation. The alpha1a-isoform is important for Na(+) uptake in freshwater, but the molecular basis for the functional differences between the two isoforms is not known. Here, three amino acid substitutions are identified in transmembrane segment 5 (TM5), TM8 and TM9 of the alpha1a-isoform compared to the alpha1b-isoform, and the functional consequences are examined by mutagenesis and molecular modeling on the crystal structures of Ca-ATPase or porcine kidney Na,K-ATPase. In TM5 of the alpha1a-isoform, a lysine substitution, Asn783 --> Lys, inserts the epsilon-amino group in cation site 1 in the E(1) form to reduce the Na(+)/ATP ratio. In the E(2) form the epsilon-amino group approaches cation site 2 to force ejection of Na(+) to the blood phase and to interfere with binding of K(+). In TM8, a Asp933 --> Val substitution further reduces K(+) binding, while a Glu961 --> Ser substitution in TM9 can prevent interaction of FXYD peptides with TM9 and alter Na(+) or K(+) affinities. Together, the three substitutions in the alpha1a-isoform of Na,K-ATPase act to promote binding of Na(+) over K(+) from the cytoplasm, to reduce the Na(+)/ATP ratio and the work done in one Na,K pump cycle of active Na(+) transport against the steep gradient from freshwater (10-100 microM: Na(+)) to blood (160 mM: Na(+)) and to inhibit binding of K(+) to allow Na(+)/H(+) rather than Na(+)/K(+) exchange. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
Complementary Index |
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