Fig. 3. Identification of the egl-4 gene. (A) Physical map of the egl-4 region, related genomic clones, exon-intron organization of F55A8.2 and structure of mRNAs. Black boxes indicate protein-coding regions. Red boxes represent 5' extensions of exon 8 in mRNAs for a2 and b2. (B) Amino acid sequences of PKGa1 and PKGb1 predicted by the cDNAs. They differ only in the N termini (the sequence of a1 is the upper line). Underlines denote a glycine-rich domain, two cGMP binding domains and a kinase domain. Double underlines denote putative NLS (see Discussion). (C) Schematic of the primary structure of the EGL-4(PKGa1) protein and the mutation sites. Blue box represents the glycine-rich domain.