The Na,K-ATPase or sodium pump is an integral membrane protein found in the plasma membrane of virtually all animal cells. It exists as an alphabeta heterodimer for which several isoforms have been described. During its reaction cycle, the sodium pump extrudes three Na+ ions from the cell in exchange for two extracellular K+ ions using the energy of hydrolysis of one ATP molecule. The electrochemical sodium gradient generated provides the driving force for secondary solute transport. Structure/function analysis of the catalytic subunit, alpha, provides strong evidence for interactions between the actuator domain which comprises the cytoplasmic N-terminus and the M2--M3 loop, and the M4--M5 loop containing the ATP binding and phosphorylation sites. This thesis describes two major aspects of Na,K-ATPase structure and function. First, the role of the unique N-terminus of the ubiquitous al isoform of the rat Na,K-ATPase in E1/E2 conformational transitions is investigated as this region extends beyond that of the well-characterized and related SERCA pump for which high resolution structures have been obtained. Furthermore, the N-terminus is the region of greatest primary sequence diversity among the otherwise homologous alpha1, alpha2 and alpha3 isoforms. The results provide strong evidence for a self-regulatory domain within the N-terminus that modulates conformational transitions via novel intramolecular interactions within the N-terminus and between the N-terminus and regions within the cytoplasmic M2--M3 and M4--M5 loops. Another aspect of this thesis concerns a comparative study of the isoform-specific ligand affinity differences. For this study, the alpha2 and alpha3 isoforms were compared with the ubiquitous alpha1 isoform. The results demonstrate that alpha3-specific ligand affinities can be explained by its distinct reactivities with alkali cations, as well as by differences in the rates of partial reactions. The distinct kinetics of a
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.84432 |
| Date | January 2003 |
| Creators | Segall, Laura |
| Contributors | Blostein, Rhoda (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biochemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001975451, proquestno: AAINQ88576, Theses scanned by UMI/ProQuest. |
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