Mapping of Interdomain Interfaces Required for the Functional Architecture of Yor1p, a Eukaryotic ATP-binding Cassette (ABC) Transporter

Abstract

ATP-binding cassette (ABC) transporters are a large superfamily of proteins that mediate substrate translocation across biological membranes. Our goal was to define the intramolecular interactions that contribute to quaternary assembly of a eukaryotic ABC transporter and determine how the architecture of this protein influences its biogenesis within the secretory pathway. We used chemical cross-linking approaches to map interdomain interactions in the yeast ABC transporter, Yor1p, which functions as a pleiotropic drug pump at the plasma membrane. We have defined interactions between the two nucleotide-binding domains (NBDs) and between the NBDs and specific intracellular loops (ICLs) that are consistent with current structural models of bacterial ABC exporters. Furthermore, we detected relatively weak NBD-NBD and ICL-ICL interactions that may correspond to transient sites of cross-talk between domains required for coupling of ATP hydrolysis with substrate translocation. Mutation of a key residue in ICL2 caused misassembly of the altered protein, leading to increased sensitivity to the mitochondrial poison, oligomycin. We identified intragenic suppressing mutations that rescued the oligomycin resistance associated with this aberrant protein and demonstrated that the suppressing mutations restored multiple interdomain interfaces. Together, our biochemical and genetic approaches contribute to a greater understanding of the architecture of this important class of proteins and provide insight into the quality control surveillance that regulates their biogenesis and deployment within the eukaryotic cell. ATP-binding cassette (ABC) transporters are a large superfamily of proteins that mediate substrate translocation across biological membranes. Our goal was to define the intramolecular interactions that contribute to quaternary assembly of a eukaryotic ABC transporter and determine how the architecture of this protein influences its biogenesis within the secretory pathway. We used chemical cross-linking approaches to map interdomain interactions in the yeast ABC transporter, Yor1p, which functions as a pleiotropic drug pump at the plasma membrane. We have defined interactions between the two nucleotide-binding domains (NBDs) and between the NBDs and specific intracellular loops (ICLs) that are consistent with current structural models of bacterial ABC exporters. Furthermore, we detected relatively weak NBD-NBD and ICL-ICL interactions that may correspond to transient sites of cross-talk between domains required for coupling of ATP hydrolysis with substrate translocation. Mutation of a key residue in ICL2 caused misassembly of the altered protein, leading to increased sensitivity to the mitochondrial poison, oligomycin. We identified intragenic suppressing mutations that rescued the oligomycin resistance associated with this aberrant protein and demonstrated that the suppressing mutations restored multiple interdomain interfaces. Together, our biochemical and genetic approaches contribute to a greater understanding of the architecture of this important class of proteins and provide insight into the quality control surveillance that regulates their biogenesis and deployment within the eukaryotic cell. ATP-binding cassette (ABC) 3The abbreviations used are: ABCATP-binding cassetteCFTRcystic fibrosis transmembrane conductance regulatorERendoplasmic reticulumERADER-associated degradationMSDmembrane-spanning domainNBDnucleotide-binding domainTMHtransmembrane helixICLintracellular loopHAhemagglutininGFPgreen fluorescent protein. transporters are integral membrane proteins that translocate substrates across biological membranes using a mechanism that couples ATP binding/hydrolysis with transport. Full ABC transporters, from prokaryote to human, share a global structure composed of two cytoplasmic nucleotide-binding domains (NBDs) that contain conserved regions involved in ATP binding/hydrolysis and at least two membrane-spanning domains (MSDs). Despite the remarkable conservation of architecture across kingdoms, the physiology of membrane transport mediated by ABC transporters is extremely diverse. ABC transporters can act as either exporters or importers and handle a vast array of molecules, including ions, polysaccharides, vitamins, lipids, and peptides, with each transporter relatively specific for a given set of ligands. The quaternary organization of ABC transporters is of great interest to gain further insight into both the shared molecular mechanisms governing the function of ABC transporters and the specificity and directionality of substrate transport. ATP-binding cassette cystic fibrosis transmembrane conductance regulator endoplasmic reticulum ER-associated degradation membrane-spanning domain nucleotide-binding domain transmembrane helix intracellular loop hemagglutinin green fluorescent protein. The architecture of ABC transporters also has important implications for human health because ABC transporters play roles in drug resistance, ion transport, and other fundamental physiological processes. Mutations in a single ABC transporter, the cystic fibrosis transmembrane regulator (CFTR) cause cystic fibrosis in humans as a result of inappropriate chloride transport across epithelial membranes (1Riordan J.R. Rommens J.M. Kerem B. Alon N. Rozmahel R. Grzelczak Z. Zielenski J. Lok S. Plavsic N. Chou J.L. Drumm M.L. Iannuzzin M.C. Collins F.S. Tsui L.-C. Science. 1989; 245: 1066-1073Crossref PubMed Scopus (5977) Google Scholar). Many disease-related mutations in CFTR cause the protein to improperly assemble within the endoplasmic reticulum (ER) (2Kopito R.R. Physiol. Rev. 1999; 79: S167-S173Crossref PubMed Scopus (375) Google Scholar), resulting in engagement of an ER quality control process that prevents deployment of misfolded proteins. However, the nature of the aberrant assembly that triggers the quality control checkpoint remains poorly understood (3Seibert F.S. Jia Y. Mathews C.J. Hanrahan J.W. Riordan J.R. Loo T.W. Clarke D.M. Biochemistry. 1997; 36: 11966-11974Crossref PubMed Scopus (66) Google Scholar, 4Seibert F.S. Linsdell P. Loo T.W. Hanrahan J.W. Clarke D.M. Riordan J.R. J. Biol. Chem. 1996; 271: 15139-15145Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar, 5Seibert F.S. Linsdell P. Loo T.W. Hanrahan J.W. Riordan J.R. Clarke D.M. J. Biol. Chem. 1996; 271: 27493-27499Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar). Thus, a comprehensive understanding of the quaternary structure of ABC transporters may provide insight into the folding defect(s) induced by disease-related mutations and might facilitate the design of novel therapeutic strategies. A large body of biochemical data, complemented more recently by crystal structures of several prokaryotic ABC transporters, reveals that several important domain-domain interfaces govern the quaternary structure of ABC transporters (6Linton K.J. Physiology (Bethesda). 2007; 22: 122-130Crossref PubMed Scopus (254) Google Scholar). Interaction of the two MSDs within the lipid bilayer creates the substrate-binding pocket and the translocation channel. Similarly, the two cytoplasmic NBDs interact with each other to create two composite ATP-binding pockets (7Hopfner K.P. Karcher A. Shin D.S. Craig L. Arthur L.M. Carney J.P. Tainer J.A. Cell. 2000; 101: 789-800Abstract Full Text Full Text PDF PubMed Scopus (812) Google Scholar, 8Smith P.C. Karpowich N. Millen L. Moody J.E. Rosen J. Thomas P.J. Hunt J.F. Mol. Cell. 2002; 10: 139-149Abstract Full Text Full Text PDF PubMed Scopus (682) Google Scholar, 9Chen J. Lu G. Lin J. Davidson A.L. Quiocho F.A. Mol. Cell. 2003; 12: 651-661Abstract Full Text Full Text PDF PubMed Scopus (438) Google Scholar, 10Zaitseva J. Jenewein S. Wiedenmann A. Benabdelhak H. Holland I.B. Schmitt L. Biochemistry. 2005; 44: 9680-9690Crossref PubMed Scopus (84) Google Scholar, 11Fetsch E.E. Davidson A.L. Proc. Natl. Acad. Sci. U. S. A. 2002; 99: 9685-9690Crossref PubMed Scopus (118) Google Scholar, 12Loo T.W. Bartlett M.C. Clarke D.M. J. Biol. Chem. 2002; 277: 41303-41306Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar, 13Mense M. Vergani P. White D.M. Altberg G. Nairn A.C. Gadsby D.C. EMBO J. 2006; 25: 4728-4739Crossref PubMed Scopus (155) Google Scholar). The recent crystal structures of full prokaryotic transporters (14Locher K.P. Lee A.T. Rees D.C. Science. 2002; 296: 1091-1098Crossref PubMed Scopus (934) Google Scholar, 15Pinkett H.W. Lee A.T. Lum P. Locher K.P. Rees D.C. Science. 2007; 315: 373-377Crossref PubMed Scopus (240) Google Scholar, 16Hollenstein K. Frei D.C. Locher K.P. Nature. 2007; 446: 213-216Crossref PubMed Scopus (405) Google Scholar, 17Dawson R.J. Locher K.P. Nature. 2006; 443: 180-185Crossref PubMed Scopus (1095) Google Scholar, 18Dawson R.J. Locher K.P. FEBS Lett. 2007; 581: 935-938Crossref PubMed Scopus (347) Google Scholar, 19Ward A. Reyes C.L. Yu J. Roth C.B. Chang G. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 19005-19010Crossref PubMed Scopus (654) Google Scholar) suggest that intracellular loops (ICLs) that extend from the MSDs to interact with the NBDs may for the between domains that couples ATP binding/hydrolysis to substrate transport. a design of which extend the structure of the into the that are by to the membrane and interact with the The bacterial transporters, and are by of two with the of with the of the R.J. Locher K.P. Nature. 2006; 443: 180-185Crossref PubMed Scopus (1095) Google Scholar, 19Ward A. Reyes C.L. Yu J. Roth C.B. Chang G. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 19005-19010Crossref PubMed Scopus (654) Google Scholar). to as may for the of the two of the biochemical by the have demonstrated that domain is also involved in the quaternary structure of the eukaryotic transporters, and CFTR K.J. J. 2007; PubMed Scopus Google Scholar, L. L. Riordan J.R. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). the crystal structure of the bacterial and are in that the the of the (14Locher K.P. Lee A.T. Rees D.C. Science. 2002; 296: 1091-1098Crossref PubMed Scopus (934) Google Scholar, 16Hollenstein K. Frei D.C. Locher K.P. Nature. 2007; 446: 213-216Crossref PubMed Scopus (405) Google Scholar). We Yor1p, a yeast ABC transporter, as a to the biogenesis of this important of proteins in which both genetic and biochemical approaches S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar). is a plasma membrane protein that as a drug pump to from the and is required for resistance to the mitochondrial poison, oligomycin. the domain and as CFTR and and we have that the between and is to that in the two human of a residue within to the to in the ER and by ER-associated degradation this of the between and to that for Bartlett M.C. Loo T.W. Clarke D.M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus (84) Google Scholar). this we the quaternary structure of Yor1p, using biochemical and genetic approaches to that a architecture with to interfaces. We that interactions between specific are in the quaternary structure of ABC Furthermore, we the in associated with of folding to a to a in CFTR and intragenic that the folding of this aberrant protein. and at in yeast and or yeast and with for sensitivity to to and to yeast and that with oligomycin used in this are in in was a from of was the for using to hemagglutinin used in cross-linking and to create the was a from and an of green fluorescent protein to the of this was the for to the of the was by a of the also a from of to and to S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar). in and with or as a in for at by and in of to of of by to for and proteins by to and by using of to and to in in of and into was with a of or for was by of to and for by to and the of by by using an or in to and using a with and a with the and using cross-linking has to a for in the of domains in a of ABC transporters T.W. Bartlett M.C. Clarke D.M. J. Biol. Chem. 2002; 277: 41303-41306Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar, 13Mense M. Vergani P. White D.M. Altberg G. Nairn A.C. Gadsby D.C. EMBO J. 2006; 25: 4728-4739Crossref PubMed Scopus (155) Google Scholar, K.J. J. 2007; PubMed Scopus Google Scholar, L. L. Riordan J.R. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar, Bartlett M.C. Loo T.W. Clarke D.M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus (84) Google Scholar). We have used this to define interactions between MSDs in S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar). We to extend this to define interdomain interactions that govern the quaternary structure of to determine the global architecture of a eukaryotic ABC We used the crystal structures of bacterial transporters, with of and or CFTR as a to the of specific within both the NBDs and which contribute to cross-linking in the of the protein S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar). we to which demonstrated that single with with the of Furthermore, of single and the function of Yor1p, as by in oligomycin resistance and biochemical from several ABC transporters that the two NBDs of a full transporter are in a to and that at least to create an with two composite ATP-binding pockets by the of and an of the (7Hopfner K.P. Karcher A. Shin D.S. Craig L. Arthur L.M. Carney J.P. Tainer J.A. Cell. 2000; 101: 789-800Abstract Full Text Full Text PDF PubMed Scopus (812) Google Scholar, 8Smith P.C. Karpowich N. Millen L. Moody J.E. Rosen J. Thomas P.J. Hunt J.F. Mol. Cell. 2002; 10: 139-149Abstract Full Text Full Text PDF PubMed Scopus (682) Google Scholar, 9Chen J. Lu G. Lin J. Davidson A.L. Quiocho F.A. Mol. Cell. 2003; 12: 651-661Abstract Full Text Full Text PDF PubMed Scopus (438) Google Scholar, 10Zaitseva J. Jenewein S. Wiedenmann A. Benabdelhak H. Holland I.B. Schmitt L. Biochemistry. 2005; 44: 9680-9690Crossref PubMed Scopus (84) Google Scholar, 11Fetsch E.E. Davidson A.L. Proc. Natl. Acad. Sci. U. S. A. 2002; 99: 9685-9690Crossref PubMed Scopus (118) Google Scholar, 12Loo T.W. Bartlett M.C. Clarke D.M. J. Biol. Chem. 2002; 277: 41303-41306Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar, 13Mense M. Vergani P. White D.M. Altberg G. Nairn A.C. Gadsby D.C. EMBO J. 2006; 25: 4728-4739Crossref PubMed Scopus (155) Google Scholar). gain structural insight into the organization of the NBDs in Yor1p, we at specific in to the sites used to the interactions the composite and the of CFTR M. Vergani P. White D.M. Altberg G. Nairn A.C. Gadsby D.C. EMBO J. 2006; 25: 4728-4739Crossref PubMed Scopus (155) Google Scholar). that of at of A of of and of to a with and the of was by and more and are from the protein. to of a with a a with was detected for the and A and the NBDs of to for CFTR M. Vergani P. White D.M. Altberg G. Nairn A.C. Gadsby D.C. EMBO J. 2006; 25: 4728-4739Crossref PubMed Scopus (155) Google Scholar). Furthermore, residue of the of also cross-linking with in the of The specificity of interactions is by the that detected between and as by the structural of the of P.C. Karpowich N. Millen L. Moody J.E. Rosen J. Thomas P.J. Hunt J.F. Mol. Cell. 2002; 10: 139-149Abstract Full Text Full Text PDF PubMed Scopus (682) Google Scholar). gain more the of involved in the NBD-NBD of Yor1p, we the to in the of with and between the the composite was the was to the and with that using the cross-linking in the of the Furthermore, we detected cross-linking in the of which to suggest that the domain and the of a relatively that are the regions of the two by the more because cross-linking was in the of of and was with the structure of prokaryotic that the quaternary architecture of ABC transporters involved specific interactions between the and the two NBDs R.J. Locher K.P. Nature. 2006; 443: 180-185Crossref PubMed Scopus (1095) Google Scholar) The of each of the transporter is to a of the of its The coupling helix also to interact with a loop the of the the coupling helix of the with the a relatively large The of interactions to conserved in eukaryotic interactions between and and ICL2 and have for and CFTR K.J. J. 2007; PubMed Scopus Google Scholar, L. L. Riordan J.R. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). We to interdomain interactions for the quaternary structure of Yor1p, and into by to correspond to the sites of We the of by in cross-linking as we the cross-linking of single which to with with the single of residue in was to with the coupling loop of which an this residue was altered to in the of the the was detected that with the and that the cross-linking detected in the single an We suggest that this an of the two domains because with and the of the cross-linking in with that with to the we also detected the with a between of the loop of and the coupling loop of was also specific for the and was detected at the of consistent with an of Furthermore, this may because we to between and residue of the coupling loop of is to result from the of to the because both to the between ICL2 and a more of the of was to two and into the coupling loop of ICL2 and was also to to the detected for both and at of and with the and We also to the using a to that and interact with their cross-talk between the two of the protein. ICL-ICL to the interdomain between and the structure that might also in with the of the of the transporter R.J. Locher K.P. Nature. 2006; 443: 180-185Crossref PubMed Scopus (1095) Google Scholar) A and between the coupling of and which both an with the of is and a may between ICL2 and which both the of the coupling of the we their to in to of using of between the we of the and cross-linking with detected for the and which correspond to or cross-linking was with the of for the a relatively weak between the coupling of and the and in a cross-linking detected in the of and by of and suggest between the coupling of and and of ICL2 and which may mediate cross-talk between the and of of interactions are in with the However, we also cross-linking between and a between the coupling of ICL2 and is as domains are to interact with However, the of two loops a of each and in a to the NBD-NBD is of a transient between the two loops associated with substrate ATP with a transient between ICL2 and cross-linking was the and interactions in that was detected in of the A Mutation in ICL2 of that play a in the domain-domain interfaces that contribute to quaternary assembly of ABC transporters is by the that mutations map to the of of of that the in the endoplasmic reticulum (3Seibert F.S. Jia Y. Mathews C.J. Hanrahan J.W. Riordan J.R. Loo T.W. Clarke D.M. Biochemistry. 1997; 36: 11966-11974Crossref PubMed Scopus (66) Google Scholar, 4Seibert F.S. Linsdell P. Loo T.W. Hanrahan J.W. Clarke D.M. Riordan J.R. J. Biol. Chem. 1996; 271: 15139-15145Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar, 5Seibert F.S. Linsdell P. Loo T.W. Hanrahan J.W. Riordan J.R. Clarke D.M. J. Biol. Chem. 1996; 271: 27493-27499Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar). mutations result in that are by the ER quality control process and to the of the We have a of genetic and biochemical to the biogenesis of and of S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar). We of to of that in the to the of function or of in sensitivity to the mitochondrial poison, oligomycin M. J. G. Mol. Cell. Biol. PubMed Scopus Google Scholar). A an of that a in ICL2 to the of was into a that a of of was to at of oligomycin resistance to the drug suggest that the the function the of We the increased oligomycin sensitivity by the was the result of protein by the using cross-linking between the and domains of with with the which to a in to detected for or that the the protein was to a molecular that to the The of or in the that the interfaces between NBDs and to that the and of share a to in the of is to cross-linking of that in the a to the folding and assembly of Yor1p, we membranes either or to by to of The of to degradation was by a and a single of with of was to a of increased to from the of sites within the aberrant of S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar). a to that of that the and of Yor1p, a shared aberrant to to determine the folding for in ER as is the for S. L. M. Lee M.C. Mol. Biol. Cell. 2007; PubMed Scopus Google Scholar), we with to its intracellular was detected at the plasma to that the induced by this can by the ER quality of of to more the nature of the and how the quaternary structure of by intragenic of the oligomycin sensitivity associated with this We that a in might the folding of the by a structural We that the of mutations our biochemical of the quaternary structure the of novel domain-domain A was and into a and that oligomycin resistance from and was to the suppressing a suppressing mutations into a by and into a to the we and that rescued the oligomycin sensitivity of mutations in regions of the of the and which are the two domains that interactions with ICL2 in the cross-linking The of suppressing mutations is of a of interdomain interactions that are by the this we the to by the by the into the of each the suppressing was to the as detected by the of and that suppressing mutations can folding and assembly associated with specific of aberrant ABC Furthermore, the of the suppressing mutations in to an our biochemical of between the also the we the suppressing mutations into the We detected for suppressing of a to the between and and We that suppressing mutations of cross-linking between and in the of a that is also in the of that the specific by mutations result in the of the of A large body of biochemical has at understanding how ABC transporters ATP binding/hydrolysis and substrate translocation across the lipid structural of several full prokaryotic ABC transporters has insight by of interdomain interactions that govern the quaternary architecture of proteins. the of interfaces in the biogenesis and function of the yeast ABC transporter Yor1p, we specific and cross-linking to the in of key We have used this to the between the to for substrate and translocation. We have the of the two NBDs of Yor1p, which to two composite ATP-binding pockets to that from the structure of the bacterial protein P.C. Karpowich N. Millen L. Moody J.E. Rosen J. Thomas P.J. Hunt J.F. Mol. Cell. 2002; 10: 139-149Abstract Full Text Full Text PDF PubMed Scopus (682) Google Scholar). architecture has also for CFTR a of molecular and chemical cross-linking M. Vergani P. White D.M. Altberg G. Nairn A.C. Gadsby D.C. EMBO J. 2006; 25: 4728-4739Crossref PubMed Scopus (155) Google Scholar). Furthermore, we have demonstrated that the of each and with the and as by the structure R.J. Locher K.P. Nature. 2006; 443: 180-185Crossref PubMed Scopus (1095) Google Scholar). also interact with the of the and The of interactions is to create an composed of two an that and an that with A and Our cross-linking of ICL2 with and by in genetic approaches that identified suppressing mutations that rescued a specific in protein, an which is rescued by the intragenic suppressing a that the genetic the that a structural is by interactions between and and the of genetic approaches in the of involved in interfaces. The in structures of both importers and is to involved in the of between MSDs and a fundamental of substrate transport that remains poorly The that the of the a structural as has given to the that interactions may important for the of the two of the protein to However, interactions to ABC the structures of bacterial ABC importers that the from the two and a mechanism of transport. of structural is that the full transporters have in the of the of how substrate influences interdomain and transport is how hydrolysis influences domain and transport. a of crystal structures have for transporters by the of structures of ABC exporters in and R.J. Locher K.P. Nature. 2006; 443: 180-185Crossref PubMed Scopus (1095) Google Scholar, 18Dawson R.J. Locher K.P. FEBS Lett. 2007; 581: 935-938Crossref PubMed Scopus (347) Google Scholar, 19Ward A. Reyes C.L. Yu J. Roth C.B. Chang G. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 19005-19010Crossref PubMed Scopus (654) Google Scholar). in of the domain-domain interactions in CFTR that the and interfaces in the of or that the of two is by ATP binding/hydrolysis L. L. Riordan J.R. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). the of substrate to of the human transporter associated with of structural ATP hydrolysis M. G. S. M. R. R. J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). we detected a weak between ICL2 and that may in the cross-talk between the two is from the prokaryotic structures and might a of that we by in of the domain-domain interactions within in the of substrate and insight into the involved in substrate transport. to their in an transporter, domain-domain interactions are for the of ABC transporters to within the cell. the aberrant induced by mutations within in the of the protein in the endoplasmic reticulum (ER) and degradation (2Kopito R.R. Physiol. Rev. 1999; 79: S167-S173Crossref PubMed Scopus (375) Google Scholar). the has to the nature of the induced by this The aberrant protein a in the of with Bartlett M.C. Loo T.W. Clarke D.M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus (84) Google Scholar), this is a of the which is in the cytoplasmic of the domain of CFTR that the the of the may the of the protein J.M. M.C. K. B. P.C. Hunt J.F. S. J. Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). has to interactions between and the which are mediated by the the between and recent cross-linking suggest that in CFTR with of the that domain-domain interfaces are the cause of misassembly of L. L. Riordan J.R. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). ER is a shared by other disease-related CFTR of which contain in the and also interdomain assembly However, the molecular that govern ER and quality control their as therapeutic The of the of disease-related mutations the of the protein and its within the to a understanding of the folding that ER quality is to the plasma that this protein is to the ER quality control a in the that the by However, the aberrant of and are to greater sensitivity to and the mutations for their to the assembly of to the oligomycin sensitivity of suggest that the ER quality control checkpoint is to in the folding between and The of the genetic and biochemical our understanding of the interactions that quaternary assembly of ABC transporters also great in the mechanisms of ER quality with