ABCC7 p.Gly241Asp
| ClinVar: |
c.721G>A
,
p.Gly241Arg
?
, not provided
|
| CF databases: |
c.721G>A
,
p.Gly241Arg
(CFTR1)
?
, Identified by DGGE and direct sequencing.
|
| Predicted by SNAP2: | A: D (66%), C: D (80%), D: D (91%), E: D (91%), F: D (91%), H: D (95%), I: D (91%), K: D (95%), L: D (85%), M: D (91%), N: D (91%), P: D (95%), Q: D (91%), R: D (95%), S: D (59%), T: D (85%), V: D (91%), W: D (95%), Y: D (91%), |
| Predicted by PROVEAN: | A: N, C: N, D: N, E: N, F: D, H: N, I: N, K: N, L: D, M: N, N: N, P: N, Q: N, R: N, S: N, T: N, V: N, W: D, Y: D, |
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[hide] Role of the extracellular loop in the folding of a... Biochemistry. 2007 Jun 19;46(24):7099-106. Epub 2007 May 22. Wehbi H, Rath A, Glibowicka M, Deber CM
Role of the extracellular loop in the folding of a CFTR transmembrane helical hairpin.
Biochemistry. 2007 Jun 19;46(24):7099-106. Epub 2007 May 22., 2007-06-19 [PMID:17516627]
Abstract [show]
The folding of membrane-spanning domains into their native functional forms depends on interactions between transmembrane (TM) helices joined by covalent loops. However, the importance of these covalent linker regions in mediating the strength of helix-helix associations has not been systematically addressed. Here we examine the potential structural impact of cystic fibrosis-phenotypic mutations in the extracellular loop 2 (ECL2) on interactions between the TM3 and TM4 helices of the cystic fibrosis transmembrane conductance regulator (CFTR) in constructs containing CFTR residues 194-241. When the effects of replacements in ECL2 (including the CF-phenotypic mutants E217G and Q220R) were evaluated in a library of wild-type and mutant TM3-ECL2-TM4 hairpin constructs, we found that SDS-PAGE gel migration rates differed over a range of nearly 40% +/- the wild-type position and that decreased migration rates correlate with increasing hairpin alpha-helical content as measured by circular dichroism spectra in sodium dodecyl sulfate micelles. The decreased mobility of TM3/4 constructs by introduction of non-native residues is interpreted in terms of an elongation or "opening" of the helical hairpin and concomitant destabilization of membrane-based helix-helix interactions. Our results support a role for short loop regions in dictating the stability of membrane protein folds and highlight the interplay between membrane-embedded helix-helix interactions and loop conformation in influencing the structure of membrane proteins.
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No. Sentence Comment
145 (iii) TM3/4 mutants G241D (38) and G241R (data not shown) migrate within 2% of WT.
X
ABCC7 p.Gly241Asp 17516627:145:20
status: NEW[hide] Non-native interhelical hydrogen bonds in the cyst... Biochemistry. 2004 Jun 29;43(25):8077-83. Choi MY, Cardarelli L, Therien AG, Deber CM
Non-native interhelical hydrogen bonds in the cystic fibrosis transmembrane conductance regulator domain modulated by polar mutations.
Biochemistry. 2004 Jun 29;43(25):8077-83., [PMID:15209503]
Abstract [show]
Polar residues comprise about 15% of the transmembrane (TM) domains of proteins, where they can stabilize structure via native side chain-side chain interhelical hydrogen bonds between TM helices. However, non-native H-bonds may be implicated in disease states, through limiting protein dynamics during transport and/or misfolding the protein by inducing non-native rotational positions about TM helical axes. Here we have undertaken an investigation of the presence and strength of H-bond interactions within a series of helix-loop-helix ("hairpin") constructs derived from TM helices 3 and 4 (italic) of the cystic fibrosis transmembrane conductance regulator (CFTR) (prototypic sequence G(194)LALAHFVWIAPLQ(207)VALLMGLIWELLQASAFAGLGFLIV(232)LALFQ(237)AGLG(241)) in which wild-type Q207 in TM3 forms an interhelical H-bond with CF-phenotypic mutant V232D in TM4 [Therien, A. G., Grant, F. E., and Deber, C. M. (2001) Nat. Struct. Biol 8, 597-601]. In the present work, a library of 21 TM3/4 constructs was prepared, where Asp residues were placed individually at TM4 positions 221-241. Using gel shift assays-in which H-bond-linked hairpins (closed conformation) migrate faster than the elongated forms (open conformation)-we found that Q207 in TM3 is able to "capture" all 21 TM4 D mutations into measurable populations of interhelical H-bonds. A similar library of TM4 D mutants-but also containing Q207L-reverted to wild-type migration rates, confirming Q207 as the polar partner for TM4 D residues. In view of the broad capture range of Q207, these results emphasize the potential consequences to folding and dynamics of introducing polar mutations into the TM domains of membrane proteins in the vicinity of a native polar TM residue.
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No. Sentence Comment
162 Thus, for example, if one assumes that I231D in TM4 forms the closest contacts with Q207 in TM3, there are 10 residues ()2.7 turns of helix) from I231D for G241D.
X
ABCC7 p.Gly241Asp 15209503:162:156
status: NEW165 Thus, the total vertical distance for the formation of an H-bond between Q207 in TM3 and G241D in TM4 will be about 15 Å (7.5 Å between the main chain carbon and the carboxamide in Q207 + 3 Å (average distance for H-bond formation) + 4.5 Å between the main chain carbon and the Asp carboxylate).
X
ABCC7 p.Gly241Asp 15209503:165:89
status: NEW166 Using standard side chain torsional angles, models indicate that such H-bond formation is physically realistic between Q207 in TM3 and G241D in TM4.
X
ABCC7 p.Gly241Asp 15209503:166:135
status: NEW180 Therefore, without Q237 (i.e., with Q237 mutated to Leu), the X f D mutants in TM4 become more open through regions encompassing A221D to G228D, and Q237D to G241D, and are ultimately unable to form an H-bond with Q207.
X
ABCC7 p.Gly241Asp 15209503:180:158
status: NEW188 Nevertheless, for any A f D or G f D mutants (in this case, A221D, A223D, G226D, G228D, A234D, A238D, G239D, and G241D), only a single-base change is required, and therefore, it is possible these mutants represent potential phenotypic CF mutants, which have yet to be discovered.
X
ABCC7 p.Gly241Asp 15209503:188:113
status: NEW