Comparison of Ths and Pyr Proteins to other signalling ligands. thisbe and pyramus genes encode proteins of 748 and 766 amino acids (aa), respectively, making them far larger than their vertebrate homolog FGF8, which is 204 aa. Branchless, another FGF ligand in Drosophila, is also a relatively large protein of 770 aa. The C-terminus is cleaved from FGF23, the only FGF family member known to be cleaved [33,34]. Dpp is produced as a 588 aa precursor, but is cleaved to primarily the TFG-β-homologous domain alone [23,28,45,46]. Spitz is processed within its transmembrane domain and, like Thisbe and Pyramus, binds to a RTK receptor to signal [23,24]. Known cleavage sites are marked with a black inverse triangle. In the Drosophila FGFs, potential cleavage sites consisting of multi-basic amino-acid motifs are marked with a white inverse triangle. Predicted N-glycosylation sites are marked with an asterisk and predicted O-glycosylation sites are marked with a vertical line.
Tulin and Stathopoulos BMC Developmental Biology 2010 10:83 doi:10.1186/1471-213X-10-83