A) MS/MS spectra of C. victoriae thyrostimulin α2-subunit tryptic fragments. The precursor ions selected for MS/MS had monoisotopic m/z of 896.43 (z=2) and 864.08 (z=3), with predicted monoisotopic m/z of 896.43 (z=2) and 864.08 (z=3), respectively. For clarity, only b and y ions are labeled. Inset b/y ladder diagrams summarize observed b- and y-ions. C; carbamidomethylated cysteine. B) The aligned precursor sequences of the α2- and β5-subunits of human, A. californica, C. victoriae, C. tessulatus and C. virgo (β5 only) thyrostimulins. Precursor signal peptides are highlighted in purple, confirmed peptide sequences are in boldface and the confirmed encoded subunits of human thyrostimulin are highlighted in blue.