Table 1.

Demonstration of protriplet amino acid homologies in 5-HT1AR–FGFR1, 5-HT1AR–5-HT2AR, and GalR1–GalR2 heterodimers.

	Galanin Set					Serotonin Set			2010 [37]		2012 [6]	2017 [34]
	VLA	NGS	GAF	LIF	LAA	SLA	VLV	DVL	LAR	SNS	AAR	LLG	TLG	QNA	RNA
5-HT1AR			+	+		+	+	+	+	+	+	+	+	+	+
FGFR1	+	+	+		+		+		+		+	+	+
GalR1	+	+	+	+	+		+		+	+		+			+
GalR2	+	+		+	+		+								+
5-HT2AR						+		+				+	+	+

Some protriplets were reported in in previous works by Borroto-Escuela et al. [6,34,37]. Others were found in lists (sets) of receptor pairs mainly involving galanin or serotonin receptors. The protriplets only exist in heterodimers and are not found in nonheterodimers. At least the majority of these protriplet homologies appear to be part of the receptor interface. (+)it refer to the presence of the protriplet in the protomer.