Nucleotide-binding domains of human cystic fibrosis transmembrane conductance regulator: detailed sequence analysis and three-dimensional modeling of the heterodimer

Abstract

The cystic fibrosis transmembrane conductance regulator (CFTR) protein is encoded by the gene that is defective in cystic fibrosis, the most common lethal inherited disease among the Caucasian population. CFTR belongs to the ABC transporter superfamily, whose members form macromolecular architectures composed of two membrane-spanning domains and two nucleotide-binding domains (NBDs). The experimental structures of NBDs from several ABC transporters have recently been solved, opening new avenues for understanding the structure/function relationships and the consequences of some disease-causing mutations of CFTR. Based on a detailed sequence/structure analysis, we propose here a three-dimensional model of the human CFTR NBD heterodimer. This model, which is in agreement with recent experimental data, highlights the specific features of the CFTR asymmetric active sites located at the interface between the two NBDs. Moreover, additional CFTR-specific features can be identified at the subunit interface, which may play critical roles in active site interdependence and are uncommon in other NBD dimers.

Phenylalanine-508 mediates a cytoplasmic–membrane domain contact in the CFTR 3D structure crucial to assembly and channel function

“…1). There are existing 3D structures of NBD1 and also a homology model of NBD2 derived from structures of NBDs of other ABC transporters (22). To arrive at a structural model of the complete CFTR, we built models of the membrane-spanning domains from the known structure of the full-length ABC exporter, Sav1866 (SI Fig.…”

“…The Homology suite from INSIGHTII (Accelrys) was used to construct an atomic model of CFTR MSDs, The x-ray structure of NBD1 (9) and an existing homology model of NBD2 (22) were used. The R domain was approximated by an ensemble of conformations derived by ab initio folding.…”

Nucleotide-binding Domains of Cystic Fibrosis Transmembrane Conductance Regulator, an ABC Transporter, Catalyze Adenylate Kinase Activity but Not ATP Hydrolysis

“…In CFTR, the NBDs are thought not to be functionally equivalent because of the lack of sequence conservation in three of the ABC transporter signature motifs (9). Similarly, biochemical reports suggest that NBD1 is a site of stable nucleotide interaction (10), whereas NBD2 has been reported to be the site of ATP hydrolysis activity (11).…”

Cystic Fibrosis Transmembrane Conductance Regulator (ABCC7) Structure

“…Several structural homology models for CFTR based on Sav1866 and Pgp have been published (Callebaut et al 2004;Mornon et al 2008Mornon et al , 2009Serohijos et al 2008). Although the two models based on Sav1866 are superficially very similar, especially in the NBD regions of the models (Callebaut et al 2004;Serohijos et al 2008), significant differences exist at the level of the individual residues, including alternative rotamers for side-chains and differing relative positions ( phasing) of amino acids in the transmembrane regions.…”

“…Although the two models based on Sav1866 are superficially very similar, especially in the NBD regions of the models (Callebaut et al 2004;Serohijos et al 2008), significant differences exist at the level of the individual residues, including alternative rotamers for side-chains and differing relative positions ( phasing) of amino acids in the transmembrane regions. These discrepancies are not surprising, because the sequence homology…”