Identification and characterization of a novel beta subunit of soluble guanylyl cyclase that is active in the absence of a second subunit and is relatively insensitive to nitric oxide.
Previously characterized soluble guanylyl cyclases form alpha-beta heterodimers that can be activated by the gaseous messenger, nitric oxide. In mammals, four subunits have been cloned, named alpha1, alpha2, beta1, and beta2. We have identified a novel soluble guanylyl cyclase isoform from the nervous system of the insect Manduca sexta that we have named M. sexta guanylyl cyclase beta3 (MsGC-beta3). It is most closely related to the mammalian beta subunits but has several features that distinguish it from previously identified soluble cyclases. Most importantly, MsGC-beta3 does not need to form heterodimers to form an active enzyme because guanylyl cyclase activity can be measured when it is expressed alone in COS-7 cells. Moreover, this activity is only weakly enhanced in the presence of the nitric oxide donor, sodium nitroprusside. Several of the amino acids in rat beta1 subunits, previously identified as being important in heme binding or necessary for nitric oxide activation, are substituted with nonsimilar amino acids in MsGC-beta3. There are also an additional 315 amino acids C-terminal to the catalytic domain of MsGC-beta3 that have no sequence similarity to any known protein. Northern blot analysis shows that MsGC-beta3 is primarily expressed in the nervous system of Manduca.
Nighorn
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Arizona Research Labs, Division of Neurobiology, The University of Arizona, Tucson, Arizona 85721, USA.
Byrnes
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KA
Morton
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DB
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000378:metabolism*; D051381:Rats; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D009569:Nitric Oxide; D006162:Guanylate Cyclase