Schematic representation of the human TWIST1 protein. (A) Multiple sequence alignments for the bHLH domain of human TWIST1 and sequences belonging to different species. Conserved residues among species are highlighted in blue blocks. The modeled mutation positions R118C, S144R and K145E are indicated by red arrows. (B) Alignment between the TWIST1_bHLH sequence and the sequences that correspond to both chains of 2QL2 dimers (C – E47 and D – NeuroD1). All of the alignments were generated by ClustalW2 with default parameters and were plotted with the BioEdit program. The symbol ”*” indicates identical amino acids between sequences and “:” indicates conserved substitutions; “.” indicates semi-conserved substitutions. The yellow blocks highlight conserved residues. Hs – Homo sapiens; Mm – Mus musculus; Xl – Xenopus laevis; Dm – Drosophila melanogaster.