Sequence and structural homology among membrane-associated domains of CFTR and certain transporter proteins.
A sequence comparison of the two membrane-associated (MA) domains of the cystic fibrosis transmembrane conductance regulator (CFTR), multidrug resistance transporter (MDR), and alpha-factor pheromone export system (STE6) proteins, each of which are believed to contain a total of 12 transmembrane (TM) segments, reveals significant amino acid homology and length conservation in the loop regions that connect individual TM sequences. Similar structural homology is observed between these proteins, hemolysin B (HLYB) and the major histocompatibility-linked peptide transporter, HAM1, the latter two which contain a single MA domain composed of six TM segments. In addition, there are specific sequences that are conserved within the TM segments of the five different membrane proteins. This observation suggests that the folding topologies of the MA domains of MDR, STE6, and CFTR in the plasma membrane are likely to be very similar. The sequence analysis also reveals that there are three characteristic motifs (a pair of aromatic residues, LTLXXXXXXP and GXXL) that are conserved in MDR, STE6, HLYB, HAM1, but not in CFTR. We propose that although CFTR may be evolutionarily related to these other membrane proteins, it belongs to a separate subclass.
Manavalan
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Genzyme Corporation, Framingham, Massachusetts 01701.
Smith
A E
AE
McPherson
J M
JM
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D008565:Membrane Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator