The crystal structure of the catalytic domain of a eukaryotic guanylate cyclase.
BACKGROUND
Soluble guanylate cyclases generate cyclic GMP when bound to nitric oxide, thereby linking nitric oxide levels to the control of processes such as vascular homeostasis and neurotransmission. The guanylate cyclase catalytic module, for which no structure has been determined at present, is a class III nucleotide cyclase domain that is also found in mammalian membrane-bound guanylate and adenylate cyclases.


RESULTS
We have determined the crystal structure of the catalytic domain of a soluble guanylate cyclase from the green algae Chlamydomonas reinhardtii at 2.55 A resolution, and show that it is a dimeric molecule.


CONCLUSIONS
Comparison of the structure of the guanylate cyclase domain with the known structures of adenylate cyclases confirms the close similarity in architecture between these two enzymes, as expected from their sequence similarity. The comparison also suggests that the crystallized guanylate cyclase is in an inactive conformation, and the structure provides indications as to how activation might occur. We demonstrate that the two active sites in the dimer exhibit positive cooperativity, with a Hill coefficient of approximately 1.5. Positive cooperativity has also been observed in the homodimeric mammalian membrane-bound guanylate cyclases. The structure described here provides a reliable model for functional analysis of mammalian guanylate cyclases, which are closely related in sequence.
Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA. wingerj@berkeley.edu
Jonathan A
JA
Winger
Emily R
ER
Derbyshire
Meindert H
MH
Lamers
Michael A
MA
Marletta
John
J
Kuriyan
D000262:Adenylyl Cyclases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D020134:Catalytic Domain; D016825:Chlamydomonas reinhardtii / Q000737:chemistry; D018360:Crystallography, X-Ray; D019281:Dimerization; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase