Guanylyl cyclases in the tropical land crab, Gecarcinus lateralis: Cloning of soluble (NO-sensitive and -insensitive) and membrane receptor forms.
cDNAs encoding three guanylyl cyclases (GCs), which catalyze the production cGMP from GTP, were cloned from the blackback land crab, Gecarcinus lateralis: the beta subunit of a NO-sensitive soluble GC (Gl-GC-Ibeta; 2380 bp; 603 amino acids; 68,435 Da), a membrane receptor GC (Gl-GC-II; 4609 bp; 1349 amino acids; 150,999 Da), and a NO-insensitive soluble GC (Gl-GC-III; 1416 bp; 285 amino acids; 32,487 Da). All three have a highly-conserved catalytic domain located in the C-terminal region and are therefore likely to be enzymatically active. Gl-GCIbeta contains heme/NO-binding (HNOB) and HNOB-associated domains characteristic of the catalytic subunit of NO-sensitive GCs. Gl-GC-II encodes a single-pass membrane protein containing ligand-binding (LB), transmembrane (TM), kinase homology (KH), and dimerization domains. Gl-GC-III is similar to Gl-GC-II but lacks the LB, TM, and most of the KH domains. Isoforms of Gl-GC-Ibeta and Gl-GC-II appear to be generated by alternative splicing. Two Gl-GC-Ibeta isoforms differed in the absence (Delta32N) or presence (Delta0N) of a 32-amino acid sequence at the N-terminus. The truncated form may not bind a heme group, but still would be able to dimerize with the alpha subunit to form a NO-insensitive enzyme. Three Gl-GC-II isoforms varied in length within the N-terminal ligand-binding domain (+18, +9, and +0 amino acid insertions). As GC-II is the putative receptor for crustacean hyperglycemic hormone (CHH), these data suggest that the isoforms differ in binding to CHH and related neuropeptides.
Lee
Sung Gu
SG
Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
Kim
Hyun-Woo
HW
Mykles
Donald L
DL