Figure 1.

Gene structure of the Ca²⁺-sensing receptor and related genes. Gene structure of the human gene is drawn on the basis of the data (8). Boxes of exon 1 and exon 6 show coding regions only. The introns of the human gene are shortened, but the Fugu genes are to scale. The Ca01 (type I) gene is the Fugu Ca²⁺-sensing receptor gene. Also shown are fragments of four metabotropic glutamate receptor genes cloned from Fugu by degenerate primer PCR. Where connecting lines are drawn to show the position of initiation codon, boundaries of introns, and the position of stop codon, this implies that they are in exactly the same position in the different genes. The shaded regions are TM sequences. All sequences of Fugu genes are deposited in the DNA Database in Japan (accession nos. AB008857–AB008866).