Susan M. E. Smith
Associate Professor and Foundation Fellow
Department of Biology & Physics
Kennesaw State University
Adjunct Assistant Professor
Department of Pathology & Laboratory Medicine
Emory School of Medicine
Office: Science Lab Bldg Rm 3004
Lab: Science Center Bldg Rm 350
Department of Biology and Physics
Kennesaw State University
1000 Chastain Road, Bldg. 12 Rm 308
Kennesaw, GA 30144 USA
My research centers around the mechanisms that control the activities
of proteins that participate in cell signaling. I use evolutionary comparisons of protein sequences
and molecular modeling to predict the parts of proteins most likely to
control their activity. And then I test those predictions in the
laboratory, using a combination of techniques to perturb and measure
activity. I investigate the structure, function and control of NADPH oxidases (Nox) and of voltage-gated proton channels (Hv1).
Noxes and Hv1 are known to work together in several cell
types, and both produce signals important not only to human health but
also to the development, physiology, and
lifestyles of many other organisms. Currently I have three excellent
undergraduate assistants and a MS student.
Hv1 Structure, Function, and Control
I use sequence analysis and
molecular models to help inform mutagenesis, electrophysiology, and other experiments investigating the control
of Hv1 activity, important to signaling in many cells and organisms.
Hv1 Molecular Model
Modeling of voltage sensor domains (VSD) is tricky because the mobility
of the S4 helix allows different alignments of the 'arginine registry'
depending on the functional state of the sensor. I used
phylogenetic analysis and a structurally informed alignment method to
fix the registry to the open state, and then Kethika Kullepumera in Régis Pomès's
lab tested two alternative homology models with massively repeated
molecular dynamics simulations. The preferred model from this
analysis produced a hypothesis about the accessibility of the third
arginine on S4, which when tested via patch clamp in Tom DeCoursey's lab turns out to be
accessible to the solution on the inside of the membrane, even in the
Hv1 Selectivity Filter -- and it wanders!
My sequence and phylogenetic analysis, combined with my molecular model, provided a good template from which to make substitutions
aimed at affecting proton conduction. The electrophysiology expertise of the DeCoursey
lab enabled us to use these mutants to find (an
essential part of) the selectivity filter of Hv1. Surprisingly,
most mutants at this site convert the perfectly proton selective Hv1 to
an anion selective channel. Also surprisingly, we can move the
selectivity filter up one turn (but not down one turn) and retain the
apparently perfect selectivity.
I developed signature sequences to predict Hv1’s in other organisms. With Al Place’s help, we found a putative Hv1 gene in a dinoflagellate cDNA
now confirmed as a bona fide Hv1 protein by patch clamping in Tom
DeCoursey's lab. In this multidisciplinary project, we are
exploring Woody Hastings’ proposal that Hv1 activity triggers the bioluminescent flash.
Here's a link about our discovery of a dinoflagellate proton channel
gene, with an illustration of how we think it works to trigger
This paper's results got picked up by
several popular science sources -- I guess everyone likes
bioluminescence! This German one makes it 'world famous': http://taz.de/Forschung-ueber-Einzeller-im-Meer/!85585/
Recent Hv1-related Publications:
C., J. Sun, C.A. Stilphen, S.M.E. Smith, H. Ocasio, B. Bermingham, S.
Darji, A. Guha, R. Patel, A.M. Geurts, H.J. Jacob, N.A. Lambert, P.M.
O’Connor. 2014. HV1 acts as a sodium sensor and promotes
superoxide production in medullary thick ascending limb of Dahl
salt-sensitive rats. Hypertension. 64, 540-50.
D., B. Musset. K. Kulleperuma, S.M.E. Smith, S. Rajan, V.V. Cherny, R.
Pomès, and T.E. DeCoursey. 2013. Peregrination of the Selectivity
Filter Delineates the Pore of the Human Voltage Gated Proton Channel
hHV1. J. Gen. Physiol. 142(6), 625-640.
K., Smith, S.M.E., Morgan, D., Musset, B., Holyoake, J., Chakrabarti,
N., Cherny, V.V., DeCoursey, T.E. & Pomès, R. (2013). Construction
and validation of a homology model of the human voltage-gated proton
channel hHV1. The Journal of General Physiology, 141(4), 445-465.
Musset, B., S.M.E. Smith, S. Rajan, D. Morgan, V.V. Cherny, and T.E. DeCoursey. (2011). Aspartate112 is the selectivity filter of the human voltage gated proton channel. Nature. 480: 273–277
Smith, S.M.E., D. Morgan, B. Musset, V.V. Cherny, A.R. Place, J.W. Hastings, and T.E. DeCoursey. (2011). A voltage-gated proton channel in a dinoflagellate.
Proceedings of the National Academy of Sciences, U.S.A. 2011
Musset, B., Smith SM, Rajan S, Cherny VV, Morgan D, DeCoursey TE. (2010). Oligomerization of the voltage gated proton channel. Channels. 4: 260-265.
Musset, B., Smith SM, Rajan S, Cherny VV, Sujai S, Morgan D, DeCoursey TE. (2010). Zinc inhibition of monomeric and dimeric proton channels suggests cooperative gating. J Physiol. 588(Pt 9):1435-49
Nox Structure, Function, and Control
I collaborate with Dave Lambeth's lab, using molecular models that I’ve
built or helped to
build to inform experiments, exploring different aspects of Nox
structure and the isoform specific control of Nox activity, fundamental
to understanding Nox's role as a signal generator. I'm involved in a project to
discover small molecule inhibitors of Noxes,
which could eventually be useful in treating diseases; others on the project include James McCoy, Yerun Zhu, Yang Li, Becky Diebold and Aiming Sun. We are also working with Shivaprakash
Gangappa at the CDC, who is testing one of our compounds in a mouse
model of influenza infection.
Recent Nox-related Publications:
B.A., S.M.E. Smith, Y. Li, J.D. Lambeth. 2014. NOX2 as a
target for Drug Development: Indications, Possible Complications and
Progress. Antioxidants and Redox Signaling. (Epub ahead of print, Mar 14 2014)
A.M., G. Szarvas, S.M.E. Smith, and E. Ligeti. 2013. Role of Rac GTPase
activating proteins in regulation of NADPH oxidase in human
neutrophils. Free Rad. Biol. Med. 68, 65-71.
Smith, SME, J Min, T Ganesh, B
Diebold, T Kawahara, Y Zhu, J McCoy, A Sun, JP Snyder, H Fu, Y Du, I
Lewis, JD Lambeth. 2012. Ebselen and congeners inhibit NADPH-oxidase 2
(Nox2)-dependent superoxide generation by interrupting the binding of
regulatory subunits. Chem. Biol. 19, 752-763
-- And a very nice write up in
the same issue of Chemistry and Biology, pointing out the innovation in
the HTS -- hats off to Tsukasa Kawahara for getting this started!
Bedard and Jaquet, 2012. Cell Free Screening for NOX Inhibitors. Chem. Biol. 19:
Kawahara, T., Jackson, H.M., Smith, S.M.E., Simpson, P.D., Lambeth, J.D. (2011). Nox5 forms a functional oligomer mediated by self-association of its dehydrogenase domain. Biochem. 50: 2013-25.
Jackson HM, Kawahara T, Nisimoto Y, Smith SM, Lambeth JD. (2010). Nox4 B-loop creates an interface between the transmembrane and dehydrogenase domains J Biol Chem. 285(14):10281-90
Short courses – I have extensive experience teaching sequence analysis
and molecular modeling to working professionals, in both short course
and workshop format. I can tailor a course or workshop to your
lab’s or organization’s needs. Contact me for details.
Examples of Older Work (Nitric Oxide Synthases; Polymerase-based methodology)
Jones RJ, Jourd'heuil D, Salerno JC, Smith SM, Singer HA. (2007). iNOS regulation by calcium/calmodulin-dependent protein kinase II in vascular smooth muscle. Am J Physiol Heart Circ Physiol. 292:H2634-42.
Ghosh, D.K., M.A. Holliday, C. Thomas, J.B. Weinberg, S.M.E. Smith, and J.C. Salerno. (2006) Nitric oxide synthase output state: design and properties of NOS oxygenase/FMN constructs. J. Biol. Chem. 281: 14173-14178.
Jones, R.J., Y.T. Gao, T. Simone, J.C. Salerno, and S.M.E. Smith. (2006) NADPH Analog binding to constitutive nitric oxide synthases activates electron transfer and NO synthesis. Nitric Oxide: Biology and Chemistry. 14: 228-237
Ingledew, W.J., S.M.E. Smith, Y.T. Gao, R.J. Jones, J.C. Salerno, and P.R. Rich. (2005) Ligand, Co-Factor And Residue Vibrations In The Catalytic Site Of Endothelial Nitric Oxide Synthase. Biochemistry. 44(11):4238-46.
Erdogan, E., Jones, R.J., Hanna, M.H., Matzlin, P., Smith, S.M.E., and J.C. Salerno (2005) INSULT, a Novel Mutagenesis Method Generating High Yields Of Closed Circular Mutant DNA With One Primer Per Mutant. Molecular
Biotechnology, 30: 21-30.
Salerno, J.C., Jones, R.J., Erdogan, E. and S.M.E. Smith (2005) A Single Stage Polymerase Based Procedure For The Introduction Of Deletions And Insertions Without Subcloning. Molecular Biotechnology, 29: 225-232.
Salerno, J.C., Harris, D.,
Irizarry, K., Morales, A., Smith, S.M.E., Roman, L., Martasek, P.,
Masters, B.S.S., Jones, C.L., Weissman, B.A., Liu, Q., and Gross, S.S.
(1997) An Autoinhibitory Control Element Defines Calcium Regulated Isoforms Of NO Synthase J. Biol. Chem. 272, 29769-29777