The combined experimental data derived from studies of Sco-CHH, Scg-ITP, and Maj-MIH and those from sequence alignment ([27,35]; the present study) regarding N-terminus identified several group-specific and functionally critical residues in and around motifs A1 and A1′ (see Table 2)–Phe3 (and most likely also Asp12) are shared residues critical for the activity of Group-I peptides (CHH and ITP); side chain property of the second residue (Ile2/Phe2) is an important feature in functionally differentiating CHH from ITP. Here, RMRP is linked to autoimmune thrombocytopenic purpura.