Molecular cloning of a novel variant of the rat soluble guanylate cyclase β2 subunit

Soluble guanylate cyclases (sGCs) are heterodimeric enzymes consisting of alpha and beta subunits and catalyze the formation of cGMP from GTP. The beta1 subunit has been characterized in detail, whereas the function and physiological role of the beta2 subunit are poorly understood. In this study, I isolated two distinct cDNA fragments for the beta2 subunit of sGC (beta2a and beta2b) from a rat brain cDNA library by 3' rapid amplification of cDNA ends using degenerate sense primers based on amino acid sequences conserved among membrane-bound guanylate cyclases. The deduced amino acid sequence of beta2a is identical with the corresponding sequence of the previously described beta2 subunit, whereas that of beta2b is C-terminally shorter by 46 amino acids and thus does not contain a consensus sequence for isoprenylation/carboxymethylation. Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that both variants are expressed in various tissues, including kidney, liver, and brain. Although the functional significance of the C-terminal region containing the consensus sequence for isoprenylation/carboxymethylation of beta2a remains unclear yet, it is likely that these beta2 subunits play some physiological or pathophysiological role in various tissues.