Fig. 4: Computational and circular dichroism analyses support a model for proline-mediated disruption of a membrane-interacting hairpin located within VLCAD’s C-terminal domain.
From: Structural basis for defective membrane targeting of mutant enzyme in human VLCAD deficiency
a AlphaFold model structure of dimeric VLCAD demonstrating residues 440–473 as a helix-turn-helix hairpin. Residues A450 and L462, two sites of proline mutagenesis in human VLCAD deficiency, are colored in blue and red, respectively. b A surface view of the predicted α-helical hairpin demonstrates a hydrophobic interface surrounded by a perimeter of positively-charged residues, including lysines 440, 442, 452, 467 and arginines 470, 471, 472. c-e Model structures (AlphaFold) for wild-type (c), A450P (d), and L462P (e) VLCAD proteins demonstrate how proline mutagenesis can disrupt the structure of the α-helical hairpin. f-h Circular dichroism (CD) of wild-type (f), A450P (g), and L462P (h) peptides corresponding to residues 440–473 of the predicted α-helical hairpin in solution and in the presence of liposomes (relative α-helicity in the presence of liposomes of 2.5:1.7:1 for wild-type:A450P:L462P). CD experiments were performed in duplicate using independent preparations of peptides with similar results.
