The long-term goal of my laboratory is to understand the molecular bases of signal transduction at the cellular level. We utilize a multifaceted approach that combines high-resolution X-ray crystallography with biochemical, biophysical, molecular biological, and genetic methods to gain insights into how signals are sensed, transduced, and more importantly, timed for generating the desired physiological response.

We are addressing several key questions related to both the generation of gaseous messengers - nitric oxide (NO), carbon monoxide (CO), and molecular oxygen (O2) - and their utilization as cellular signals. NO is particularly attractive, for it is a ubiquitous signaling molecule with diverse functions, including the maintenance of blood pressure in healthy human subjects, host defense, and neurotransmission. We have discovered that a strong parallel exists between the NO biosynthetic machinery of mammals and pathogens such as Bacillus anthracis - the etiological agent of anthrax. Utilizing a battery of structure-function approaches we are investigating if this system is: (a) part of the pathogen's armamentarium against host defense, and (b) equipped for aberrant induction of normally homeostatic pathways in the host.

We are also focusing our efforts on deciphering how binding of a gaseous ligand is structurally coupled to activation of downstream signaling events, and how this information can be garnered to aid in the rational design of novel molecules with therapeutic potential. Although significant headway has been made in understanding the mechanisms of mammalian NO biosynthesis, two decades of intense efforts have failed to provide the structural basis for how the NO signaling culminates in second messenger (cGMP) production. This is because the NO sensor (soluble guanylyl cyclase) is too scarce, too fragile, and extremely difficult to work with. We have developed novel strategies that will overcome these problems and pave the way to gain molecular insights into NO signal transduction. In addition, we have also introduced a provocative approach called 'systems biology in isolation' to study CO signaling at the organism level without interference from NO or O2. Together, results from our work inter alia will facilitate efforts to combat cardio- and cerebrovascular disorders in which alterations in gaseous messenger signal transduction directly contributes to the etiology of disease.

Another area of research in my laboratory focuses on establishing the structural bases for how novel functions evolve in proteins. There is growing consensus that 'one gene - one protein - one function' is clearly an oversimplification, for a given protein can exhibit multiple functions depending on the cellular makeup. We are utilizing a combination of genomic, directed evolution, and combinatorial chemistry-based approaches to unravel the molecular mechanisms that readily switch off one function while selectively preserving another. This work has the potential to improve our knowledge regarding how cells can recruit proteins and enzymes to perform a new task, particularly in scenarios such as tumorigenesis.