Student Theses and Dissertations

Date of Award

2003

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Thesis Advisor

Roderick MacKinnon

Keywords

ion channels, BK channels, Ca2+, K+, RCK domains

Abstract

Potassium ion channels are ubiquitously expressed from bacteria to mammals where they are involved in various processes ranging from the regulation of osmotic pressure in a single cell to the electrical response in muscle fibers to the generation of action potentials in neurons. The BK channel family (BK for Big K+ conductance) is an interesting subfamily of K+ channels responsive to both membrane voltage and intracellular calcium ion. The unique, high-affinity Ca2+ sensitivity of BK channels is critical to their physiological function in various cell types. The mechanism by which Ca2+ activates BK channel gating, however, is not well understood. Here we present a structure-based approach to the study of BK channels with the goal of providing a structural and functional model of the Ca2+-activation mechanism. Sequence analysis of BK channel C-terminal domains and domains from prokaryotic homologs reveals the conservation of unique positions defining a novel regulatory domain associated with K+ conduction, the RCK domain. Crystal structures of RCK domains from prokaryotic sources relate the conservation of sequence to the structure, assembly and function of these domains. We propose a hypothetical model for the structure and function of the C-terminal domains of BK as a set of RCK domains that conduct the Ca2+-activation mechanism. The features and constraints predicted by the RCK domain model are tested by the electrophysiological assay of a variety of human BK constructs. The results support a domain structure and assembly consistent with the proposed model for the BK C-terminus. In addition, the results identify residues and regions involved in Ca2+ activation: the Ca2+-binding event and the transduction of the binding energy through protein conformational changes to the channel domain. The RCK domain model thus provides a framework for the study of Ca2+ activation in BK channels.

Comments

A thesis presented to the faculty of The Rockefeller University in partial fulfillment of the requirements for the degree of Doctor of Philosophy

Permanent URL

http://hdl.handle.net/10209/211

License and Reuse Information

Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.

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