Guanylyl cyclases
A majority of today's medicines act via membrane bound receptors. These receptors are the communication portals for cells with mostly signals going into the cell but sometimes also signaling from the inside-out. Our lab is
mainly focusing on the natriuretic peptide receptors and related receptors which are wonderful complex signal transduction systems to tackle scientifically.
These receptors are guanylyl cyclase receptors involved in blood pressure regulation and bone growth and their activation leads to the production of the intracellular second messenger cGMP. Deciphering the molecular signaling intricacies for these receptors is our paramount focus using a battery of approaches such as protein crystallography, cell biology, biochemical, biophysical, and computational ligand design techniques.
Such receptor intricacies include ligand binding, transmembrane helix movement(s), de-phosphorylation/desensitization, ATP binding, high-low affinity state switches, kinase-homology domain regulation, and receptor activation and cGMP production. All of these steps are structurally not well understood making these receptors ideal candidates for a concerted multi-disciplinary approach to gain mechanistic insights.
We have previously determined the crystal structure of the ligand binding domain of the atrial natriuretic peptide receptor revealing many unexpected discoveries such as its structural similarity with periplasmic binding proteins, possible dual allosteric regulation, the hormone binding site, and dimer interfaces.
Our current projects range from relatively straight forward experiments such as site-directed mutagenesis and activity assays to probe specific questions, to biochemically characterizing and crystallizing the remaining individual domains, to our most ambitious long term goals of crystallizing the entire receptor and discovering new pharmaceutically interesting effectors based on our structural investigations.
Click here to view structure or download coordinates.
In addition, we have recently, in collaboration with the Warman lab, identified 12 human mutations in the c-type natriuretic peptide receptor (NPR-B or GC-B). Patients
with these mutations have a dwarf-like phenotype.
Our lab has enzymatically characterized a number of these mutants as well as generated a homology model
for the entire full length NPR-B receptor. This work was published recently in
Am. J. Human Genetics (click on Publications to find references).
Please click here to visit Dr. Matthew Warman's lab website http://genetics.case.edu/bone/
Our lab has determined the structure of an domain that is homologous to that of
of the NO binding heme domain of the soluble guanylyl cyclase receptor. .
This receptor is involved in a number of key cardiovascular and neuronaling signaling processes
and is crucial for controling for example blood pressure.
In addition to this heme domain structure, we have determined its structure in complex with nitric oxide as well as with carbon monoxide
and uncovered interesting heme pivoting/bending conformational changes that illuminate a mechanism
for NO/CO discrimination and differences in soluble guanylyl cyclase activation by these two gaseous diatomic signaling molecules. This work is in collaboration with Annie
Beuve and was recently published in EMBO J (Ma et al. 2007). A follow-up
collaborative publication in PNAS revealed that desensitization of sGC can occur via S-nitrosylation with a likely involvement of a cysteine within
the H-NOX domain (Sayed et al, 2007).
Click here to view structure or download coordinates.
We have recently determined the crystal structure of a H-NOXA/H-NOBA domain found in a Nostoc Signal Transduction
Histidine Kinase (STHK). This domain has strong homology to the PAS domain found in both subunits of the
soluble guanylyl cyclase receptor  .
Our structure revealed this
domain to be dimeric and we subsequently carried out structure-function studies in the soluble guanylyl cyclase to confirm that this latter protein also harbors a likely similar dimeric PAS dimer
structure. Our results have gained new insights into the importance of this dimerization module for overall architecture and regulation of the soluble
guanylyl cyclase receptor, a key receptor for blood pressure regulation.
This work was also in collaboration with Annie
Beuve and was recently published in JBC (Ma et al. JBC 2008).
Click here to view structure or download coordinates.
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