MOLECULAR-CLONING AND EXPRESSION OF A NEW ALPHA-SUBUNIT OF SOLUBLE GUANYLYL CYCLASE - INTERCHANGEABILITY OF THE ALPHA-SUBUNITS OF THE ENZYME

A cDNA coding for a new subunit of soluble guanylyl cyclase with a calculated molecular mass of 81.7 kDa was cloned and sequenced. On the basis of sequence homology, the new subunit appears to be an isoform of the alpha-1-subunit and was designated alpha-2 as the new subunit is very similar to the alpha-1-subunit in the middle and C-terminal part; it is quite diverse in the N-terminal part. Preceding experiments had shown that coexpression of the alpha-1- and beta-1-subunits is necessary to obtain a catalytically active guanylyl cyclase in COS cells [(1990) FEBS Lett. 272, 221-223]. The finding that the alpha-2-subunit was able to replace the alpha-1- but not the beta-1-subunit in expression experiments demonstrates the interchangeability of the alpha-subunit isoforms of soluble guanylyl cyclase.