Fig. 1.

A, GnRH-R nucleotide and predicted peptide sequences from H. burtoni. Transmembrane domains are shaded. Variant transcripts were found missing the bases between 1 and 2 and between 3 and 4 (positioned above the sequence here). Priming sites are indicated for the nested homology-based primers (underlined) and the H. burtoni-specific primers (italics). B, Comparison of predicted amino acid sequence homology among H. burtoni, several other teleost species, an amphibian (X. laevis), and a mammal, shown as percent identity. Sequence comparisons were made for the whole sequence, the amino extracellular tail alone, the whole sequence without the tails, and the carboxyl intracellular tail alone. C, Phylogenetic comparison of available cDNA sequences for GnRH-R. Note that nonmammalian sequences are separated into type I and type II (7). The H. burtoni GnRH-R reported here is type I, although an uncharacterized genomic DNA fragment (included here for comparison) aligns with type II sequences.