Research Interests: Heart Disease
Science gives us deep insights into the structure of our world and her temporal development. We can learn about natural phenomena from the past and gain insights into current assumptions. Perhaps most importantly, it provides us with critical knowledge into physical processes, leading to technology that improves the very essence of what matters most in the world – life itself. Change is constant, yet we live in a highly mechanized age in which we like to be able to predict the future. As the driver of a racing car at high speed must calculate the curves in his reaction, the speed of our future technology development requires a wide look in the future. One very important prediction is the critical importance of combining basic science and new technologies to improve and expand lives. If we focus on discovering combinations of proteins, enzymes, nucleic acids, and genes and then understand their functions, then we can learn much about how they can help molecules function better and thereby improve and expand the lives, especially of those suffering from severe health problems.
Heart disease: My research is focused on the regulation of calcium transport in the heart, which plays a major role in current hypotheses about the causes of heart failure and possible therapeutic approaches. My objectives are to gain insight into mechanisms of this regulatory function, and to develop a chemical engineering approach to control these processes. The research focuses on two proteins: the calcium pump (Ca-ATPase), and phospholamban (PLB). Ca-ATPase actively pumps Ca2+ into the lumen of the sarcoplasmic reticulum and thus relaxes the muscle cell, whereas PLB is an integral membrane protein that regulates the calcium pump in cardiac muscles.
I am a part of an interdisciplinary group of scientists in biophysics, structural biology, and biochemistry. As a chemist/biochemist my goal is to combine multidisciplinary approaches of chemical synthesis, biochemical reconstitution, functional assays, and magnetic resonance spectroscopy, to understand and control the mechanism by which PLB regulates the calcium pump. Until recently, my goal was to understand the molecular physiology of the heart. Now I am excited by our lab's new commitment to applying these biophysical principles to the development of improved therapeutic methods for the treatment of heart failure. My work plays an essential role in this effort, because EPR measurements on synthetic PLB labeled with the TOAC spin label are crucial for measuring the R/T ration, which governs the potency of PLB mutants for inhibiting SERCA.
Nature Protocols 2007
A procedure was developed for the synthetic incorporation of the spin labeled non-natural amino acid TOAC (2, 2, 6, 6-tetramethyl-piperidine-1-oxyl-4-amino-4-carboxlc acid) into the membrane protein phospholamban (PLB), coupled rigidly to the a-carbon, providing direct detection of peptide backbone dynamics by electron paramagnetic resonance (EPR).
This work demonstrated that the cytoplasmic domain of PLB is in a dynamic equilibrium between an ordered conformation, which is in direct contact with the membrane surface, and a dynamically disordered form, which is detached from the membrane and poised to interact with its regulatory target.
J Mol Biol 2006
Demonstrated by EPR spectroscopy of TOAC-PLB phosphorylation at Ser16 induced an order-to-disorder (T to R) transition in the cytoplasmic domain of PLB, and it is this dynamically disordered (hyper extended) R structural state that rises above the membrane surface and binds to the SECA cytoplasmic domain in a conformation that relieves SERCA inhibition.
J Biol Chem 2007
Using a combination of nuclear magnetic resonance, electron paramagnetic resonance, and coupled enzyme assays, we investigated how PLB mutations affect its structural dynamics and its interaction with SERCA. This work demonstrated the design of new "Loss of Function (LOF)" mutants for possible application in recombinant gene therapy (P21G-PLB with improved LOF characteristics in vitro).
J Mol Biol 2011
PLB conformational changes in combination of electron paramagnetic resonance and nuclear magnetic resonance spectroscopy were investigated. This work showed that inhibition of SERCA is carried out by the folded ground state (T state) of the PLB, while the relief of inhibition involves promotion of PLB to excited conformational states. This work supported the hypothesis that PLB population shifts (folding/unfolding) are a key regulatory mechanism for SERCA.
Biochem Biophys Res Commun 2011
This work showed in combination of FRET measurements and activity assays that two LOF PLB mutants (S16E and L31A) competed effectively with PLB for SERCA binding, relieving SERCA inhibition. These results provide a rational explanation for the success of S16E-based gene therapy in animal models of heart failure.
Lockamy, E.L., R. L. Cornea, C. B. Karim, and D. D. Thomas. 2011 Functional competition between phospholamban variants provides insight into the molecular mechanism of gene therapy for cardiomyopathy. Biochem Biophys Res Commun, accepted.
Gustavsson, M., N. J. Traaseth, C. B. Karim, E. L. Lockamy, D. D. Thomas, and G. Veglia. 2011. Lipid-mediated folding/unfolding of phospholamban as a regulatory mechanism for the sarcoplasmic reticulum calcium ATPase. J. Mol Biol, March 2011, accepted. PMC in process.
Lowman, X. H., McDonnell, M. A., Kosloske, A., Odumade, O. A., Jenness, C., Karim C., B., Jemmerson, R., and A. Kelekar. 2010. The Proapoptotic function of NOXA in human leukemia cells is regulated by the kinase Cdk5 and by glucose. Mol Cell, Dec 10; 40 (5): 823-33.
Becucci, L., R. Guidelli, C.B. Karim, D.D. Thomas, and G. Veglia. 2009. The role of sarcolipin and ATP in the transport of phosphate ion into the sarcoplasmic reticulum. Biophys J. 97: 2693-2699. PMCID: 2776249.
Becucci, L., Cembran, A., Karim, C.B., Thomas, D.D., Guidelli, R., Gao, J., and G. Veglia. On the function of pentameric phospholamban: ion channel or storage form? 2009. Biophys J. May 20; 96(10): L60-2. PMID: 19450461.
Zhang, Z., X. Xi, C. P. Scholes, and C. B. Karim. Rotational dynamics of HIV-1 nucleocapsid protein NCp7 as reported as probed by a spin label incorporated by peptide synthesis. 2008. Biopolymers (Peptide Sci), 89 (12): 1125-1135. PMID: 18690667.
Xi, X., Y. Sun, C. B. Karim, V. M. Grigoryants, and C. P. Scholes. HIV-1 Nucleocapsid protein NCp7 and its RNA stem loop 3 partner. I. Rotational dynamics of spin-labeled RNA stem loop 3. 2008. Biochemistry, 47: 10099-10110. PMID: 18729386.
Ha, N. K., N. J. Traaseth, R. Verardi, J. Zamoon, A. Cembran, C. B. Karim, D. D. Thomas , and G. Veglia. 2007. Controlling the inhibition of the sarcoplasmic Ca 2+ -ATPase by tuning phospholamban structural dynamics. J Biol Chem , 282: 37205-14. PMID: 17908690.
Traaseth, N. J., R. Verardi, K. D. Torgersen, C. B. Karim, D. D. Thomas, and G. Veglia. 2007. Spectroscopic validation of the pentameric structure of phospholamban. Proc Nat Acad Sci USA, 104: 14676-14681.
Becucci, L., R. Guidelli, C. B. Karim, D. D. Thomas, and G. Veglia. 2007. An electrochemical investigation of sarcolipin reconstituted into a mercury-supported lipid bilayer. Biophys J, 93: 2678-2687.
Nesmelov, Y. E., C. B. Karim, L. Song, P. G. Fajer, and D. D. Thomas. 2007. Rotational dynamics of phospholamban determined by multifrequency electron paramagnetic resonance. Biophys J, 93: 2805-2812.
Karim, C.B., Z. Zhang, and D.D. Thomas. 2007. Synthesis of TOAC-spin-labeled proteins and reconstitution in lipid membranes. Nature Protocols, 2: 43-49.
Zhang, Z., H.A. Remmer, D.D. Thomas and C. B. Karim. 2006. Backbone dynamics determined by electron paramagnetic resonance to optimize solid-phase peptide synthesis of TOAC-labeled phospholamban. Biopolymers (Peptide Sci), 88: 29-35.
Christine B. Karim, Zhiwen Zhang, Edmund C. Howard, Kurt D. Torgersen, and D.D. Thomas. 2006. Phosphorylation-Dependent Conformational Switch in Spin-Labeled Phospholamban Bound to SERCA. J Mol Biol, 358: 1032-40.
Zamoon, J., F. Nitu , C. B. Karim C., D. D. Thomas, and G. Veglia. 2005. Mapping the interaction surface of an integral membrane protein: unveiling the conformational switch in phospholamban regulation of SERCA. Proc Natl Acad Sci USA,102: 4747-52.
Christine B. Karim, Tara L. Kirby, Zhiwen Zhang, Yuri Nesmelov, and D.D. Thomas. 2004. Phospholamban structural Dynamics in Lipid Bilayers Probed by a Spin Label Rigidly Coupled to the Peptide Backbone. Proc Natl Acad Sci USA, 101(40): 14437-14442.
Mueller, B., C. B. Karim, I. V. Negrashov, H. Kutchai, and D.D. Thomas. 2004. Direct detection of phospholamban and SERCA interaction in membranes using fluorescence resonance energy transfer. Biochemistry, 43: 8754-8765.
Kirby, T., C.B Karim, and, D.D. Thomas. 2004. EPR reveals a large-scale conformational change in the cytoplasmic domain of PLB upon binding to the SR Ca-ATPase. Biochemistry, 42: 5842-52.
Buck, B., J. Zamoon, T.L. Kirby, T.M. DeSilva, C.B. Karim, D.D Thomas, and G. Veglia. 2003. Overexpression, purification and characterization of recombinant Ca-ATPase regulators for high-resolution solution and solid-state NMR studies. Protein Expr Purif, 30: 253-261.
Lockwood, N.A., Raymond S. Tu, Zhiwen Zhang, Matthew V. Tirrell, David D. Thomas, and Christine B. Karim. 2003. Structure and Function of Integral Membrane Protein Domains Resolved by Peptide-Amphiphiles: Application to Phospholamban. Biopolymers, 69: 283–292.
Mascioni, A., C.B. Karim, J. Zamoon, D.D. Thomas, and Gianluigi Veglia. 2002. Solid-state NMR and rigid body molecular dynamics to determine domain orientation of monomeric phospholamban. J. Am. Chem. Soc. 124: 9392-9393.
Mascioni, A., C.B. Karim, G. Barany, D.D. Thomas, and Gianluigi Veglia. 2002. Structure and orientation of sarcolipin in lipid environments. Biochemistry 41: 475-482.
Karim, C.B., M.G. Paterlini, L.G. Reddy, G.W. Hunter, G. Barany, and D.D. Thomas. 2001. Role of cysteine residues in structural stability and function of a transmembrane helix bundle. J. Biol. Chem. 276: 38814-38819.
Hellstern, S., S. Pegoraro, C.B. Karim, A. Lustig, D.D. Thomas, L. Moroder, and J. Engel. 2001. Sarcolipin, the shorter homologue of phospholamban, forms oligomeric structures in detergent micelles and in liposomes. J. Biol. Chem. 276: 30845-30852.
Karim, C.B., C.B. Marquardt, J. D. Stamm, G. Barany, and D. D. Thomas. 2000. Synthetic null-cysteine phospholamban analogue and the corresponding transmembrane domain inhibit the Ca-ATPase. Biochemistry 39: 10892-10897.
Karim, C. B., L.G. Reddy, G.W. Hunter, Y.M. Angell, G. Barany, and D.D. Thomas. 2000. Chemical approach for evaluating role of the cysteine residues in pentameric phospholamban structure: Effect on sarcoplasmic reticulum Ca2+-ATPase. In Peptides for the New Millennium: Proceedings of the Sixteenth American Peptide Symposium (Gregg B. Fields, James P. Tam, and George Barany, eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 381-382.
Karim, C.B., J.D. Stamm, J. Karim, L.R. Jones, and D.D. Thomas. 1998. Cysteine reactivity and oligomeric structure of phospholamban and its mutants. Biochemistry 37: 12074-12081.
Thomas, D.D., L.G. Reddy, C.B. Karim, M. Li, R.L. Cornea, J.M. Autry, L.R. Jones, and J. Stamm. 1998. Direct spectroscopic detection of molecular dynamics and interactions of the calcium pump and phospholamban. Ann. N. Y. Acad. Sci. 853: 186-195.
Steinhoff, H-J. and C.B. Karim. 1993. Protein dynamics and EPR-spectroscopy: Comparison of molecular dynamic simulations with experiments. Ber. Bunsen Ges. Phys. Chem. 97: 163-171.
Steinhoff, H-J., O. Dombrowsky, C.B. Karim, and C. Schneiderhahn. 1991. Two dimensional diffusion of small molecules on protein surfaces: An EPR study of the restricted translational diffusion of protein-bound spin labels. Eur. Biophys. J. 20: 293-303.
Karim, C.B., R. Philipp, W.E. Trommer, and J.H. Park. 1989. Interaction of glyceraldehyde-3-phosphate dehydrogenase with AMP as studied by means of a spin-labeled analog. Biol. Chem., Hoppe-Seyler 370: 1245-1252.
Fleischer, S., C. Karim, J.O. McIntyre, R. Mink, J. H. Park, B. Rudy, P. Vogel, J. Wiese, A. Wolf, and Wolfgang E. Trommer. 1986. Structure-function relationships in F1-ATPase and dehydrogenases as studied by spin-labeled nucleotides. Bull. Magn. Reson. 8: 197-198.
Karim, C.B., A.H. Beth, S. Fleischer, J.O. McIntyre, R. Mink, J.H. Park, B.H. Robinson, R.T. Wilder, and W.E. Trommer. 1986. Studies of structure function relationships in dehydrogenases by means of the spin-labeling technique. Biol. Chem. Hoppe-Seyler 367: 88.