University of Iowa
Department of Biochemistry
4-403 BSB
Iowa City, IA 52242-1109 USA phone: 877-846-8569
or 319-335-7932
fax: (319) 335-9570
biochem@uiowa.edu

Department of Biochemistry

Professor of Biochemistry, PhD

Office: 4-450 BSB
Phone: (319) 335-7885
Fax: (319) 335-9570
madeline-shea@uiowa.edu

Madeline A. Shea
51 Newton Rd
Biochemistry/Univ. of Iowa
Iowa City, IA 52242

Research Interests

This laboratory probes the linkage between cooperative ligand binding, conformational change and enzyme activation by calmodulin, a regulatory calcium- binding protein. Calmodulin is the primary eukaryotic intracellular calcium receptor and serves as a second messenger to regulate cellular responses to transient calcium fluxes. It is clinically relevant for human physiology (for example, it is a target of anti-psychotic drugs) and is also found in plants and fungi. Cooperative binding of four calcium ions to calmodulin causes large conformational changes; these changes control the sites and extent of calmodulin activation of important cellular enzymes and structural proteins (see Figure).

In order to determine the states that are functionally significant in this complex network of interactions, it is necessary to develop and apply new methods to directly determine energetic and structural properties of calcium binding. Quantitative proteolytic footprinting and applications of multi-dimensional heteronuclear NMR are capable of monitoring individual residues or bonds during a titration representative of a cellular influx of calcium. These studies have shown that the two domains of calmodulin interact in different ways as calcium fills the four sites of the protein.

Calcium-dependent structural rearrangements of calmodulin also are monitored by changes in the fluorescence, circular dichroism and hydrodynamic properties. These combined approaches are aimed at elucidating molecular mechanisms of cooperativity in calmodulin by determining the differences in intrinsic binding affinity at the four calcium-binding sites of calmodulin and the extent and nature of inter- and intra-domain cooperativity. To dissect these interactions, we are studying the isolated domains of calmodulin and many mutants shown to have phenotypic effects on complexes of calmodulin with its target enzymes.

Computational molecular modeling is used to visualize and calculate properties of these proteins and serves as a complement to the experimental studies of ligand- linked conformational change. The goal is to combine energetic and structural data to formulate models that will explain how synchronized changes in calcium levels modulate many diverse physiological processes.

Recent Publications

Erickson, J.R., Joiner, M.L., Guan X., Kutschke, W., Wang, J., Oddis, C.V., Bartlett, R.K., Lowe, J.S., O'Donnell, S., Aykin-Burns, N., Zimmerman, M.C., Zimmerman, K., Ham, A.L., Weiss, R.M., Spitz, D.R., Shea, M.A., Colbran, R.J., Mohler, P.J., Anderson, M. (2008) Direct Oxidation Results in Ca²⁺ Independent Activation of CaMKII Cell (accepted, January 28).

Theoharis, N.T., Sorensen, B.R., Shea, M.A. (2008) Neuronal Voltage?Dependent Sodium Channel Type II (NaV1.2) IQ Motif Lowers Calcium Affinity of the C?domain of Calmodulin Biochemistry 47: 112-123 (http://dx.doi.org/10.1021/bi7013129) (12 pp)

Newman, R.A., VanScyoc, W.S., Jaren, O.R., and Shea, M.A. (2007) Domain-Specific Interactions of Calmodulin with Melittin: Peptide Docks with the C-domain of Apo CaM but Preferentially Increases Calcium Binding Affinity of the N-domain. (in press, Proteins: Structure, Function, Bioinformatics). (http://dx.doi.org/10.1002/prot.21861) (21 pp)

Akyol, Z., Gakhar, L., Sorensen, B.R., Hell, J.W., and Shea, M.A. (2007) The NMDA Receptor NR1 C1 Region Bound to Calmodulin: Structural Insights into Functional Differences between Homologous Domains. (PDB entry:? 2HQW) Structure 15: 1603-1617 (http://dx.doi.org/10.1016/j.str.2007.10.012) (15 pp)

Li, Q., Cooper, J.J., Altwerger, G.H., Feldkamp, M.D., Shea, M.A., and Price, D.P. (2007) HEXIM1 is a promiscuous double-stranded RNA-binding protein and interacts with RNAs in addition to 7SK in cultured cells.? Nucleic Acids Research 35: 2503?2512. (http://dx.doi.org/10.1093/nar/gkm150) (10 pp)

Merrill, M.A., Malik, Z., Akyol, Z., Bartos, J.A., Leonard, A.S., Hudmon, A., Shea, M.A. and Hell, J.W. (2007) Displacement of a-Actinin from the NMDA Receptor NR1 C0 Domain by Ca2+/Calmodulin Promotes CaMKII Binding.? Biochemistry 46:8485-97 (http://dx.doi.org/10.1021/bi0623025) (13 pp)

VanScyoc, W.S., Newman, R.A., Sorensen, B.R., Shea, M.A. (2006) Calcium Binding to Paramecium Calmodulin Mutants Having Domain?Specific Effects on Regulation of Ion Channels.? Biochemistry 45: 14311-14324 (http://dx.doi.org/10.1021/bi061134d) (14 pp)

Ross JBA, Laws W, Shea M.? (2006) Intrinsic Fluorescence in Protein Structure Analysis. in Protein Structures: Methods in Protein Structure and Structure Analysis: Luinescence Spectroscopy and Circular Dichroism, Eds. VN Uversky, EA Permyakov, Nova Science Publishers, Inc., New York. 55-72 ISBN 1600214045 (http://www.vanstockum.nl/product/7188809/Methods-In-Protein-Structure-And-Stability-Analysis.html) (18 pp)

Wang, B., Martin, S.R, Newman, R.A., Hamilton, S.L., Shea, M.A., Bayley, P.M., and Beckingham, K. (2004) Biochemical properties of V91G calmodulin: A calmodulin point mutation that deregulates muscle contraction in Drosophila.? Protein Science 13 3285-3297 (http://dx.doi.org/10.1110/ps.04928204) (13 pp)

Hines, R., Sorensen, B.R., Shea, M.A., Maury, W. (2004) PU.1 Binding to ets Motifs within the Equine Infectious Anemia Virus Long Terminal Repeat (LTR) Enhancer: Regulation of LTR Activity and Virus Replication in Macrophages J. Virology 78: 3407?3418. (http://dx.doi.org/10.1128/JVI.78.7.3407-3418.2004) (12 pp)

Akyol, Z., Bartos, J., Jaren, O.R., Faga, L., Shea, M.A. and Hell, J.? (2004) Apo-Calmodulin Binds with its COOH-terminal Domain to the N-methyl-D-aspartate Receptor NR1 C0 Region J. Biol. Chem. 279(3): 2166-2175. (http://dx.doi.org/10.1074/jbc.M302542200 (10 pp)

Faga, L.A., Sorensen, B.R., VanScyoc, W.S., and Shea, M.A. (2003) Basic Interdomain Boundary Residues in Calmodulin Decrease Calcium Affinity of Sites I and II by Stabilizing Helix-Helix Interactions Proteins:? Structure, Function & Genetics 50: 381-391. (http://dx.doi.org/10.1002/prot.10281) (11 pp)

Leonard, A.S., Bayer, K-U, Merrill, M., Shea, M.A., Schulman, H., and Hell, J.W. (2002) Regulation of CaMKII Docking to NMDA Receptors by Calcium/Calmodulin and a-Actinin J. Biol. Chem. 277: 48441-48448 (http://dx.doi.org/10.1074/jbc.M205164200)? (8 pp)

Jaren, O.R., Kranz, J.K., Sorensen, B.R., Wand, A.J., Shea, M.A. ?(2002) Calcium-Induced Conformational Switching of Paramecium Calmodulin: Changes in the Protein Backbone Observed by Heteronuclear NMR Studies. Biochemistry 41: 14158-14166. (http://dx.doi.org/10.1021/bi026340+) (9 pp)

VanScyoc, W.S., Sorensen, B.R., Rusinova, E., Laws, W., Ross, J.B.A., and Shea, M.A. (2002) Domain-Specific Fluorescence of Calmodulin: Phenylalanine Reports Exclusively on Calcium Binding to the N-Domain Biophysical Journal 83: 2767-2790. (http://dx.doi.org/10.1529/biophysj.102? (24 pp)

Xiong, L-W, Newman, R.A., Rodney, G.C., Thomas, O., Zhang, J-Z, Persechini, A., Shea, M.A., and Hamilton, S.L. (2002) Lobe Dependent Regulation of Ryanodine Receptor Type One by Calmodulin J. Biol. Chem. 277:40862?40870. (http://dx.doi.org/10.1074/jbc.M206763200) (9 pp)

Sorensen, B.R., Faga, L.A., Hultman, R., Shea, M.A. (2002)? Interdomain Linker Increases Thermostability and Decreases Calcium Affinity of Calmodulin N-Domain. Biochemistry 41: 15-20. (http://dx.doi.org/10.1021/bi011718+) (6 pp)

Sun, H., Yin, D., Coffeen, L.A., Shea, M.A., and Squier, T.C. (2001) Mutation of Tyr138 Disrupts the Structural Coupling Between the Opposing Domains in Vertebrate Calmodulin. Biochemistry 40:9605-9617. (http://dx.doi.org/10.1021/bi0104266) (13 pp)

VanScyoc, W. and Shea, M.A. (2001) Phenylalanine fluorescence studies of calcium binding to N-domain fragments of Paramecium calmodulin mutants show increased calcium affinity correlates with increased disorder. Protein Science 10:1758-1768. (http://dx.doi.org/10.1110/ps.11601) (11 pp)

Sorensen, B.R., Eppel, J.T., Shea, and M.A. (2001) Paramecium Calmodulin Mutants Defective in Ion Channel Regulation Associate with Melittin in the Absence of Calcium but Require it for Tertiary Collapse.? Biochemistry 40:896-903. (http://dx.doi.org/10.1021/bi0023091) (8 pp)

Affiliations

Biochemistry Department