A novel, conserved and possibly functional motif “WHWGHTW” in mitochondrial transcription across Bilateria

•The intergenic regions of mitogenomes may have functional and/or regulatory roles that have yet to be identified.•Here, we bioinformatically investigated and characterised the motif of “WHWGHTW” in nd4L- (X) - trnT gene cluster in mitogenome across 1889 species from Bilateria.•This motif can be functional especially in mitochondrial transcription because of its reverse complementarity to a previously described DmTTF binding sequence (Roberti et al., 2006, Roberti et al., 2003).•The motif is remarkable because of its possession of G and T nucleotides in the fourth and sixth positions, and, the bias on T and G nucleotides instead of C and A in the degenerated positions.