Daphnia pulex Trk amino acid sequence. Amino acid positions are numbered on the left. The putative signal sequence cleavage site is indicated by an arrowhead. Leucine-rich motifs are in italics and flanking cysteine clusters in bold. Both Ig-like domains are underlined; conserved asparagines with structural roles for ligand binding are in grey and double underlined. The transmembrane region is underlined by a thick line. The first phosphorylation site by cAMP/cGMP-dependent kinase proteins, RYS is shown with a black background, as is the tyrosine responsible for Shc recruitment. Within the tyrosine kinase domain (boxed), the lysine responsible for ATP binding and the second phosphorylation site by cAMP/cGMP-dependent kinase proteins, RKFT, are shown by a black background. The autophosphorylation sequence (DIYSSDYYK) is highlighted in grey and the autophosphorylated tyrosines are shown on a black background. The tyrosine responsible for PLC gamma docking is underlined and in larger font.