Guanylate cyclase involved in the production of the second messenger cGMP (By similarity). Regulates chemotaxis responses toward Na(1+) and Li(1+) salt ions and alkaline pH in ASE left (ASEL) sensory neuron. Directly senses environmental alkalinity in ASEL neuron which probably leads to the activation of cGMP-gated cation channel tax2/tax4 (PubMed:23664973, PubMed:19523832). GTP = 3',5'-cyclic GMP + diphosphate Homodimer. Localizes in cilium of ASEL sensory neurons. Expressed asymmetrically in ASEL sensory neuron. The extracellular domain is required for the direct sensing of alkaline pH. The protein kinase domain is predicted to be catalytically inactive. Belongs to the adenylyl cyclase class-4/guanylyl cyclase family. Extended N-terminus.