Dhakshnamoorthy B, Rohaim A, Rui H, Blachowicz L, Roux B. Structural and functional characterization of a calcium-activated cation channel from Tsukamurella paurometabola.
Nat Commun 2016;
7:12753. [PMID:
27678077 PMCID:
PMC5052707 DOI:
10.1038/ncomms12753]
[Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 07/25/2016] [Indexed: 02/03/2023] Open
Abstract
The selectivity filter is an essential functional element of K+ channels that is highly conserved both in terms of its primary sequence and its three-dimensional structure. Here, we investigate the properties of an ion channel from the Gram-positive bacterium Tsukamurella paurometabola with a selectivity filter formed by an uncommon proline-rich sequence. Electrophysiological recordings show that it is a non-selective cation channel and that its activity depends on Ca2+ concentration. In the crystal structure, the selectivity filter adopts a novel conformation with Ca2+ ions bound within the filter near the pore helix where they are coordinated by backbone oxygen atoms, a recurrent motif found in multiple proteins. The binding of Ca2+ ion in the selectivity filter controls the widening of the pore as shown in crystal structures and in molecular dynamics simulations. The structural, functional and computational data provide a characterization of this calcium-gated cationic channel.
Tetrameric cationic channels specificity is determined by the sequence and structural conformation of their selectivity filter. Here, the authors show that a cationic channel from Tsukamurella paurometabola is non-selective due to a Ca2+-binding motif within its unusual proline-rich filter.
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