WES of 4 pedigrees and description of SRP54 mutations. (A) Confirmation of SRP54 mutations by Sanger sequencing of DNA extracted from whole blood sample and fibroblasts. *Individuals analyzed by WES. (B) Exon-intron of the SRP54 gene locus and protein diagram with the positions of all the mutations identified in this study. (C) Ribbon representation of the three-dimensional structure of the human SRP54 (gold)/SRα (pink) dimer (pdb 5l3q) in 2 different orientations, with the positions of the 7 mutated amino acids (sphere and ball-and-stick representations on the left and right, respectively). The 2 molecules of GMPPNP (5′-guanylyl-imidodiphosphate), a nonhydrolyzable GTP analog are shown. The positions of the 5 G elements are reported in green (G1) and red (G2-G5). Magnesium ions are shown as green balls. For a detailed description of the contacts and interactions made by the 7 mutated amino acids, see supplemental Data.