Smita Mohanty

Associate Professor

University of Delhi, Ph.D., 1988

University of Washington,

Postdoctoral Research Associate, 1991-1993.

Department of Chemistry and Biochemistry

Auburn University

Auburn, AL 36849-5312

(334)844-7081

mohansm@auburn.edu

Biochemistry, Structural Biology, Molecular Biology, and Computational Chemistry: 
Cloning, expression, purification and 3-dimensional structure determination of proteins by NMR and X-ray crystallography, mutagenesis and functional studies of proteins involved in cancer, various signaling pathways and many diseases.

Awards

PECASE (Presidential Early Career Award for Scientist and Engineers) - 2000

POWRE award from NSF-October 2000 

Research Summary

Our research interest has focused on structure-function studies of proteins using high-resolution solution NMR, circular dichroism (CD) and fluorescence spectroscopy techniques. It is amazing to see the relationship between the primary sequence of a protein to its 3-dimensional structure that defines specificity as well as diversity in its functions and how even a point mutation can sometimes disrupt or modify the functions of a protein causing in many instances abnormalities or diseases. To get a view of protein structure, function and mode of interactions at a molecular level, we use high resolution solution NMR, circular dichorism (CD), fluorescence techniques along with biochemical, molecular biology (cloning, mutagenesis) and computational chemistry.

Thus molecular biology, biochemistry, protein chemistry, biophysical chemistry (NMR and other techniques) and computational chemistry are used in our laboratory to understand and correlate the structure-functions of both soluble and membrane bound proteins. Several projects are currently in progress in our laboratory. Research work in our laboratory is supported by funding from NSF, USDA and NIH.

Congenital Disorders of Glycosylation

We are investigating the molecular mechanisms of function of an extremely important eukaryotic membrane bound enzyme “oligosaccharyltransferase (OST)”. Oligosaccharyltransferase is a membrane associated multimeric enzyme located in the endoplasmic reticulum (ER) and is involved in co-translational N-linked glycosylation of nascent protein. Genetic defects in OST cause a series of clinical problems known as congenital disorders of glycosylation (CDG) that includes mental retardation, developmental delay, hypoglycemia, dysmorphic features, anorexia etc. Complete loss is lethal for all animals. Our group is actively involved in the structure-function studies of both yeast and human Oligosaccharyltransferase enzymes. The 3-dimensional structures of proteins are essentially “blueprints” for the development of a chemical compound to be a successful drug. Our group has already solved the 3-dimensional solution structure of the first eukaryotic yeast OST subunit, Ost4p (shown below).

(A) Stereo view of the ensemble of the 20 lowest energy NMR structures of Ost4p (B) Ribbon view of the structure of Ost4p. (C) Ost4p structure in membrane (D) Structure of Ost4p from the restricted molecular dynamics calculation in a water/octane/water simulation cell. Octane molecules in grey, water molecules in red and white. (E) Location of the mutation-sensitive residues on the helix a2, viewed along the helix axis. (F) Model of Stt3p-Ost4p-Ost4p complex

Moreover, we have cloned, successfully overexpressed, and purified the most critical OST subunit, Stt3p. Structural and functional characterization of Stt3p containing the catalytic site of OST enzyme along with that of other yeast and human OST subunits is in progress in our laboratory. These studies will provide insight into the mechanisms of function of this essential and critical enzyme.

Human PDZ domain and Tumorigenesis

Glutaminase-interacting protein (GIP) is a small 14 kDa protein containing a single PDZ domain. GIP was originally identified in a yeast two-hybrid genetic selection system in human brain while looking for interactors of glutaminase. GIP is directly involved in the modulation of tumor growth through regulation of glutaminase and b-catenin. In addition, we have found that GIP interacts with the cell surface protein FAS, which belongs to tumor necrosis factor (TNF) receptor family and mediates cell apoptosis. Apart from glutaminase, b-catenin and FAS, a plethora of binding partners has been reported implicating GIP in key biological processes. Indeed, all the signal transduction pathways involving GIP can lead to cancer when unregulated. Interestingly, GIP regulates many of these signaling processes through its PDZ domain. Because PDZ proteins have well-defined binding sites, they are promising targets for drug discovery. Furthermore, GIP is one of the smallest members of the PDZ family, containing only one PDZ domain that represents its full primary structure, thus offering it as a very suitable candidate for structural studies. Structure, function, and interaction studies of GIP with different binding partners will provide us the insight into the mechanisms of action of this multifunctional protein, which is indeed a necessary prelude for successful drug design. Our investigation into structure, function, kinetics, dynamics, and interaction studies of GIP with different binding partners will provide the insight into the mechanisms and role of this PDZ domain containing human protein plays in recognition, signaling and tumorigenesis, which is essential for successful drug design.

Signal Transduction in Olfaction

We have made great progress in understanding the mechanisms of odor detection in lepidopteran moth by the olfactory receptor using the proteins of “smell” or odorant binding protein (OBP). Our solution NMR structure of an OBP revealed the details of the odorant-binding site and provided the first insight into the nature of the odor uptake mechanism at neutral pH. Moreover, from the NMR structure of this protein at acidic pH, we reported a novel mechanism of odor release, triggered by the protonation of key histidine residues near the olfactory neuron where the membrane potential decreases the local pH. Our current research efforts are focused to test the above model of ligand release by mutational studies and to address the question of molecular recognition and mechanisms of substrate specificity by OBPs of different moth species.

ApolPBP Binding cavity ApolPBP acetate binding site

Publications

Uma V. Katre, Suman Mazumder, Rabi K. Prusti, and Smita Mohanty, Ligand Binding Turns Moth Pheromone-binding Protein into a pH Sensor: Effect On The Antheraea Polyphemus PBP1 Conformation,  Journal of Biological Chemistry ,  2009 , 284 (46), 32167-32177.

Monimoy Banerjee, Chengdong Huang, Javier Marquez, and Smita Mohanty, Probing the structure, function and dynamics of human gulataminase-interacting protein (GIP): A possible target for drug design, Biochemistry, 2008, 47 (35), 9208-9219.

Monimoy Banerjee, Erich Meyerowitz, Chengdong Huang & Smita Mohanty, Probing the Conformation and Dynamics of Allatostatin Neuropeptides: A Structural Model for Functional Differences, Peptides, 2008, 29(3):375-385.

Priscilla Ward, Chengdong Huang, Monimoy Banerjee & Smita Mohanty, Interaction of Metal Ions with Glutaminase Interacting Protein (GIP): A Potential Role of GIP in Brain Diseases, Spectroscopy, 2008, Volume 22, No. 4, page 213-221

Joshua Ring, Rabi K. Prusti & Smita Mohanty, Chemical Communication: A visit with insects, Current Chemical Biology, 2008, 2, Number 1, 83-96.

S. Zubkov, A. Gronenborn, I. L. Byeon & S. Mohanty, Structural consequences of the pH-induced conformational switch in A. polyphemus pheromone-binding protein: mechanisms of ligand release, Journal of Molecular Biology, 2005, 354, 1081-1090.

S. Mohanty, S. Zubkov & A. Gronenborn, Solution NMR structure of Antheraea polyphemus PBP provides new insight into pheromone recognition by pheromone binding proteins, Journal of Molecular Biology, 2004, 337, 443-451.

S. Zubkov, W. J. Lennarz & S. Mohanty, Structural basis for the function of a novel minimembrane protein subunit of yeast oligosaccharyltransferase Proc. Natl. Acad. Sci. U.S.A, 2004 101, issue 11, 3821-3826.

Smita Mohanty, Sergey Zubkov and Ramon Campos-Olivas, 1H, 13C and 15N backbone assignments of the pheromone binding protein from the silk moth Antheraea polyphemus (ApolPBP). J. Biomol. NMR, 2003, 27, 393.