ABCMdb

ABCC7 p.Gly85Ala

ClinVar:	c.254G>A , p.Gly85Glu D , Pathogenic c.254G>T , p.Gly85Val ? , not provided
CF databases:	c.254G>A , p.Gly85Glu D , CF-causing ; CFTR1: This mutation was detected in family #26, a French Canadian family classified as PI. This Gly to Glu change is associated with a group IIb haplotype. The mutation destroys a Hinfl site. The PCR product derived from the 3i-5 and 3i-3 primers is cleaved by this enzyme into 3 fragments, 172, 105, and 32 bp, respectively, for the normal sequence; a fragment of 277 bp would be present for the mutant sequence. They analyzed 54 CF chromosomes, 8 from group II and 50 normal chromosomes, 44 from group II and did not find another eample of G85E. c.254G>T , p.Gly85Val (CFTR1) ? , The patient with G85V carried G542X on the other chromosome, and presented mild phenotype with PI.
Predicted by SNAP2:	A: D (95%), C: D (95%), D: D (95%), E: D (59%), F: D (95%), H: D (95%), I: D (95%), K: D (95%), L: D (95%), M: D (95%), N: D (95%), P: D (95%), Q: D (95%), R: D (95%), S: D (95%), T: D (95%), V: D (95%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: N, C: D, D: D, E: D, F: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: N, T: D, V: D, W: D, Y: D,

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[hide] Alteration of CFTR transmembrane span integration ... Mol Biol Cell. 2011 Dec;22(23):4461-71. Epub 2011 Oct 12. Patrick AE, Karamyshev AL, Millen L, Thomas PJ
Alteration of CFTR transmembrane span integration by disease-causing mutations.
Mol Biol Cell. 2011 Dec;22(23):4461-71. Epub 2011 Oct 12., [PMID:21998193]

Abstract [show]
Many missense mutations in the cystic fibrosis transmembrane conductance regulator protein (CFTR) result in its misfolding, endoplasmic reticulum (ER) accumulation, and, thus, cystic fibrosis. A number of these mutations are located in the predicted CFTR transmembrane (TM) spans and have been projected to alter span integration. However, the boundaries of the spans have not been precisely defined experimentally. In this study, the ER luminal integration profiles of TM1 and TM2 were determined using the ER glycosylation machinery, and the effects of the CF-causing mutations G85E and G91R thereon were assessed. The mutations either destabilize the integrated conformation or alter the TM1 ER integration profile. G85E misfolding is based in TM1 destabilization by glutamic acid and loss of glycine and correlates with the temperature-insensitive ER accumulation of immature full-length CFTR harboring the mutation. By contrast, temperature-dependent misfolding owing to the G91R mutation depends on the introduction of the basic side chain rather than the loss of the glycine. This work demonstrates that CF-causing mutations predicted to have similar effects on CFTR structure actually result in disparate molecular perturbations that underlie ER accumulation and the pathology of CF.

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No. Sentence Comment
170 To investigate whether the mutant effects on folding and TM boundaries are caused by the loss of glycine or by the introduction of the ionizable group, the 85 and 91 positions were mutated to the neutral residue alanine (G91A and G85A). Login to comment
172 In the ECL-site assay, G91A and G85A N-terminal deletion constructs were glycosylated until a 14-residue deletion was partially glycosylated and a 16-residue deletion was not glycosylated (Figure 6A). Login to comment
173 L88 is at the edge of the TM1 ER integration profile edges for both G91A and G85A (Figure 6B), which are shifted by two or three residues from the WT TM1 ER integration profile edge. Login to comment
175 The two-residue boundary shifts are consistent with the substitution for glycine causing a small but consistent decreased distance between the ECL1 site and the ER membrane. It is striking that the G85A TM1 glycosylation pattern does not indicate multiple profiles for TM1, indicating that the aberrant pattern of G85E TM1 results from introduction of the glutamate side chain (Figure 6A). Login to comment
176 Role of the ionizable side chain in trafficking of G91R and G85E The data from the glycosylation assay demonstrate that the G85E mutant splits the integration profile of TM1, whereas the G91R, G85A, and G91A mutants do not. Login to comment
181 However, G85A was not assessed in the Xenopus system. Login to comment
182 In stark contrast to G91A, G85A accumulates in the ER, suggesting that both introduction of charge and loss of glycine at position 85 contribute to G85E ER accumulation. Login to comment
186 At the lower temperature, both G91R and G85A mutants partially traffic from the ER and are thus temperature sensitive, similar to ΔF508. Login to comment
235 HeLa cell trafficking of WT, ΔF508, G85E, G85A, G91R, and G91A mutant CFTR at 37°C was analyzed by Western blot analysis (A). Login to comment
240 Figure 6: Experimental TM1 ER luminal integration profile edges for G91A and G85A mutant CFTR. Login to comment
241 (A) Core glycosylation analysis of G91A and G85A mutant CFTR containing the artificial ECL1 site by deletion of residues between the glycosylation site and TM1. Login to comment
244 (B) A combined schematic of the experimentally identified TM1 ER integration profiles for the G91A and G85A mutants. Login to comment
264 Furthermore, the G85A nonpolar mutation does not perturb the TM1 integration profile and continues to cause CFTR ER accumulation. Login to comment
269 Experiments designed to test the role of Derlin-1 in the recognition of the G85A mutant would be a reasonable future step toward distinguishing between these two models. Login to comment
286 The mutations G91R, G91A, G85E, and G85A were introduced into CFTR constructs containing the natural, artificial, and deletion mutants on the artificial site. Login to comment