article 1 for discussion quiz

article 1 for discussion quiz - ARTICLES 2005 Nature...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
VOLUME 12 NUMBER 1 JANUARY 2005 17 The F508 cystic fibrosis mutation impairs domain- domain interactions and arrests post-translational folding of CFTR Kai Du 1 , Manu Sharma 1,2 1,2 Misfolding accounts for the endoplasmic reticulum–associated degradation of mutant cystic fibrosis transmembrane conductance regulators (CFTRs), including deletion of Phe508 ( F508) in the nucleotide-binding domain 1 (NBD1). To study the role of Phe508, the de novo folding and stability of NBD1, NBD2 and CFTR were compared in conjunction with mutagenesis of Phe508. F508 and amino acid replacements that prevented CFTR folding disrupted the NBD2 fold and its native interaction with NBD1. F508 caused limited alteration in NBD1 conformation. Whereas nonpolar and some aliphatic residues were permissive, charged residues and glycine compromised the post-translational folding and stability of NBD2 and CFTR. The results suggest that hydrophobic side chain interactions of Phe508 are required for vectorial folding of NBD2 and the domain-domain assembly of CFTR, representing a combined co- and post-translational folding mechanism that may be used by other multidomain membrane proteins. The functional diversity of the eukaryotic proteome stems, in part, from the evolutionary appearance of multidomain proteins generated by gene duplication and exon shuffling 1 . A substantial fraction of these polypeptides are integral membrane proteins with critical transport, signaling or enzymatic activities. Although point mutations have been identified in many hereditary diseases that lead to misfolding or mis- assembly of membrane proteins 2 , little is known about the in vivo fold- ing mechanism of multidomain polypeptides 3 . Cystic fibrosis (CF) is the most common lethal genetic disease in the Caucasian population 4 . It is caused by mutations in the CF gene, which encodes CFTR, a cAMP-regulated chloride channel that belongs to the ATP-binding cassette (ABC) transporter super family 5 . CFTR contains four domains in two symmetrical halves, each com- prising a membrane-spanning domain (MSD1 and MSD2) with six transmembrane segments and an NBD (NBD1 and NBD2) with ATP hydrolytic capacity 5,6 . The two halves are connected by the fifth, reg- ulatory (R) domain 5 , which in coordination with the NBDs regu- lates the gating of CFTR 6 . The newly synthesized CFTR undergoes conformational maturation at the endoplasmic reticulum (ER), which requires cytoplasmic ATP 7 and association with cytosolic and ER chaperones 8 . The deletion mutation F508 CFTR in NBD1 is responsible for 66% of CF cases and can be identified in 90% of CF alleles 4 . The F508 mutation results in premature degradation of the channel via the ubiquitin-proteasome pathway at the ER 9–11 , probably owing to its temperature-sensitive folding defect 12 . The impaired transepithelial salt and water movements and compromised regulatory functions of CFTR
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/22/2009 for the course BIO 320 taught by Professor Staff during the Fall '08 term at University of Texas at Austin.

Page1 / 9

article 1 for discussion quiz - ARTICLES 2005 Nature...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online