Naturally occurring atrial natriuretic peptide (ANP) hormones bind and activate the cell membrane bound pGC-A receptor (particulate guanylyl cyclase receptor A). Activated pGC-A converts intracellular GTP (guanosine triphosphate) to the secondary messenger cGMP (cyclic guanosine monophosphate), thus leading to vasodilation, diuresis, natriuresis, increased glomerular filtration rate, and renal protective processes. Dr. John C. Burnett, M.D., of the Mayo Clinic is an expert in developing the specific properties of natriuretic peptides as treatments for cardiovascular and metabolic disease. Our work uses co-crystallization to visualize the molecular interaction between these natriuretic peptides and the pGC-A receptor. These atomic-resolution structures will support the design of new therapeutics for cardiorenal diseases. This work is in collaboration with John C. Burnett, M.D., of the Mayo Clinic.

Project Leader: James Zook

Proteins that are embedded in the cellular membrane are the molecular interface of drug/cell and host/pathogen relationships, however these proteins are highly technically challenging for scientific studies. Atomic resolution structures of dozens of membrane proteins have been accomplished only in the presence of conformation-dependent antibody fragments. These special antibodies enable protein structure determination (crystallization; cryo-electron microscopy) by specifically recognizing three-dimensional epitopes of the membrane-embedded protein. In collaboration with the Biodesign Center for Innovations in Medicine, we developed a unique DNA-based immunization technology that allows direct, in-membrane presentation of the protein antigen to the immune system in order to produce conformation dependent antibody ligands for structure determination of proteins that are central to pain disorders, allergy, asthma, Parkinson’s disease, schizophrenia, fatty liver diseases, cystic fibrosis, malaria, tularemia and viral pathogeneses. These antibodies will allow achievement of novel atomic-level images of membrane proteins, which will in turn reveal mechanisms that underlie human immune and neurological dysfunctions and pathogen evasion of the immune system, and will also enable development of structure-based therapeutics. Unique functional antibodies resulting from these methods will also serve as leads for antibody-based therapeutics and biosimilars.

Project Leader: Debbie T. Hansen

This is a collaborative research with Dr. William Cance, a surgeon oncologist and deputy director for the Cancer Center in Phoenix. Our interest is focused on the focal adhesion kinase (FAK), a tyrosine kinase that is a critical survival signal in cancer and a promising therapeutic target being evaluated in several clinical trials using kinase enzyme inhibitors. We are targeting the FAT-FAK domain to develop high potent inhibitors with the ultimate goal of inhibit FAK in cancer. In addition, we are working on determining the high-resolution structure of the entire kinase, which will allow us to better understand the “activation” and “inactivation” mechanisms as well as target recruitment mechanisms of FAK at a molecular level. To achieve our goals we are using X-ray crystallography at synchrotrons and X-ray free electron lasers (XFELs).

Project Leader: Jose Martin-Garcia

One of the four classes of reaction centers (RCs), the Type I anoxygenic RC, is found in an organism called Heliobacterium modesticaldum which is isolated from volcanic soils in Iceland. Their RC-antenna complex, hereafter referred to as the heliobacterial photosystem (HbP), was not well-understood until our recently collaboration that led to an X-ray crystal structure at 2.2 angstrom-resolution. We are currently using X-ray crystallography to understand various structural aspects of the HbP which gives insight into how photosynthesis evolved from an anoxygenic atmosphere on Earth.

Project Leader: Raimund Fromme

Taspase1 (threonine aspartase 1) is an endopeptidase that is overexpressed in primary human cancers, which has been identified as a potentially potent anticancer drug target. Taspase1 is a target of the NCI Experimental Therapeutics (NExT) Chemical Biology Consortium (CBC) drug development pipeline and several promising Taspase1 inhibitors have already been identified in high throughput screens. To better understand how the existing inhibitors interact with the full- length, active enzyme, and to gain an understanding of how substrates are recognized by this protease, our goal is to determine high resolution structures of the full- length, enzymatically active Taspase1 as well as structures of the active enzyme with substrates/inhibitors developed by the CBC. We are the only group in the world working on this protease so that there is no competition in the drug discovery arena!

Project Leader: Jose Martin-Garcia

There are no FDA-approved treatments for non-alcoholic fatty liver disease (NAFLD), the most common chronic liver ailment in the U.S. This disease develops independently of alcohol consumption and can lead to irreversible liver damage. NAFLD results from dysregulation of lipid breakdown in the body, the biochemical causes of which are still poorly understood. The Jun Liu lab at the Mayo Clinic recently identified the G0S2 (G0/G1 switch gene 2) protein as a selective inhibitor of adipose triglyceride lipase (ATGL), another key protein in lipid regulation and one that specifically converts triglycerides to free fatty acids. Atomic-resolution structures of G0S2, ATGL, and their interaction will reveal novel mechanisms of lipid regulation and allow structure-based design of drugs to disrupt the G0S2-ATGL interaction and thus treat NAFLD. This work is in collaboration with Jun Liu, M.D., Ph.D., of the Mayo Clinic.

Project Leader: James Zook

Membrane-embedded proteins are critical to the establishment, survival and persistence of pathogens in the host. However, for many pathogens, there is a complete lack of atomic-resolution structures representing membrane-embedded proteins. To achieve a more complete understanding of the mechanisms of immune evasion by pathogens, we are pursuing structures of membrane proteins from the causative agents of Lyme disease, tularemia, and other bacterial and viral diseases. These structures will open up a new class of protein targets to the structure-based design of anti-infectives.

Project Leader: Debbie T. Hansen and James Zook

G protein-coupled receptor kinase 6 (GRK-6) is one of seven GRKs mediating cellular responses to a variety of signals, including small molecules, peptides and proteins. It has been shown that the mRNA and protein expression of GRK6 are significantly higher in human multiple myeloma cancer cells compared to normal tissues. Screens for small molecule cancer treatments have identified numerous potential ligands that inhibit GRK6 expression in cancer cells. Our research focuses on visualizing the molecular interaction between these ligands and GRK-6 in co-crystallizations. These structures will provide significant insight into the mechanisms and kinetics of ligand-GRK6 binding and will provide a platform for structure-based drug design to treat multiple myeloma. This work is in collaboration with Nathalie Meurice, Ph.D., and A. Keith Stewart, M.B., Ch.B., of the Mayo Clinic.

Project Leader: Tien Olson