Structural dynamics of soluble chloride intracellular channel protein CLIC1 examined by amide hydrogen-deuterium exchange mass spectrometry.

Full Abstract

Chloride intracellular channel protein 1 (CLIC1) functions as an anion channel in plasma and nuclear membranes when its soluble monomeric form converts to an integral-membrane form. The transmembrane region of CLIC1 is located in its thioredoxin-like domain 1, but the mechanism whereby the protein converts to its membrane conformation has yet to be determined. Since channel formation in membranes is enhanced at low pH (5 to 5.5), a condition that is found at the surface of membranes, the structural dynamics of soluble CLIC1 was studied at pH 7 and at pH 5.5 in the absence of membranes by amide hydrogen-deuterium exchange mass spectrometry (DXMS). Rapid hydrogen exchange data indicate that CLIC1 displays a similar core structure at these pH values. Domain 1 is less stable than the all-helical domain 2, and, while the structure of domain 1 remains intact, its conformational flexibility is further increased in an acidic environment (pH 5.5). In the absence of membrane, an acidic environment appears to prime the solution structure of CLIC1 by destabilizing domain 1 in order to lower the activation energy barrier for its conversion to the membrane-insertion conformation. The significantly enhanced H/D-exchange rates at pH 5.5 displayed by two segments (peptides 11-31 and 68-82) could be due to the protonation of acidic residues in salt bridges. One of these segments (peptide 11-31) includes part of the transmembrane region which, in the solution structure, consists of helix alpha1. This helix is intrinsically stable and is most likely retained in the membrane conformation. Strand beta2, another element of the transmembrane region, displays a propensity to form a helical structure and has putative N- and C-capping motifs, suggesting that it too most likely forms a helix in a lipid bilayer.

Author information

Author/s: Stoychev, Stoyan H (SH); Nathaniel, Christos (C); Fanucchi, Sylvia (S); Brock, Melissa (M); Li, Sheng (S); Asmus, Kyle (K); Woods, Virgil L (VL); Dirr, Heini W (HW);

Affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 250, South Africa.

Grants: AI068730 (Agency:NIAID NIH HHS) ; AI072106 (Agency:NIAID NIH HHS) ; AI076961 (Agency:NIAID NIH HHS) ; AI081982 (Agency:NIAID NIH HHS) ; AI2008031 (Agency:NIAID NIH HHS) ; CA099835 (Agency:NCI NIH HHS) ; CA118595 (Agency:NCI NIH HHS) ; GM020501 (Agency:NIGMS NIH HHS) ; GM037684 (Agency:NIGMS NIH HHS) ; GM066170 (Agency:NIGMS NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Biochemistry (Biochemistry), published in United States. (Language: eng)

Reference: 2009-Sep; vol 48 (issue 35) : pp 8413-21

Dates: Created 2009/09/01; Completed 2009/09/25; Revised 2009/09/30;

PMID: 19650640, status: MEDLINE (last retrieval date: 10/1/2009, IMS Date: )

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