- B.A., 1973, Tabor College
- Ph.D., 1981, Iowa State University
- National Institutes of Health Postdoctoral Fellow, University of Pennsylvania, 1982-84
Areas of Specialization
Biophysics, spectroscopy, bioanalytical chemistry, protein interactions and dynamics, single-molecule spectroscopy
Physical, biophysical, and bioanalytical chemistry: single-molecule and time-resolved investigations of dynamics and function of biomolecules, fluorescence detection of biomolecules.
The high sensitivity in single-molecule fluorescence spectroscopy is opening new doors to understanding the structure, dynamics, and interactions of biomolecules. Conventional methods measure the average properties of many molecules, often missing important information about the distributions of structures, dynamics, and interactions. By probing single-molecules, the properties of individual members of a distribution can be measured, thus recovering lost information. The applications are profound for biophysical properties (structure and dynamics) and bioanalysis (e.g. detection of protein-protein interactions). The newest frontier, to detect and track the dynamics and interactions of single molecules inside live cells, bridges the fields of chemistry, biology, and physics.
My laboratory is particularly interested in calcium signaling proteins. The protein calmodulin functions as a molecular switch by detecting calcium signals and relaying the signal to dozens of other proteins in the cell. By detecting single molecules we obtain unique information that helps us unravel the mechanisms by which proteins like calmodulin function. Our single-molecule studies focus on calmodulin at three levels.
First, we have detected conformational states and dynamics of calmodulin freely diffusing in solution. Second, we have detected binding of calmodulin to target peptides with single-molecule sensitivity. Third, we have detected binding of calmodulin to target enzymes such as a calcium pump. In each case, single-molecule methods have revealed new intermediate states and dynamics, providing insight into how these molecules function. New projects are aimed at applying these methods in living cells.
Other research in my laboratory is aimed at detecting domain motions in proteins and peptides. Ultrafast laser pulses and high time-resolution detection are used to detect reorientational dynamics on the time scales of molecular tumbling, intramolecular motions, or fast protein domain motions. We are also using time-resolved fluorescence methods to develop new techniques for ultrasensitive fluorescence detection of substrate binding to DNA or proteins.
Carey K. Johnson, Mangala R. Liyanage, Kenneth D. Osborn, and Asma Zaidi, Single-protein dynamics and the regulation of the plasma-membrane Ca2+ pump, in Cell Signaling Reactions: Single-Molecular kinetic Analysis, Y. Sako and M. Ueda, eds. (Springer, Dordrecht, 2011) pp 121 – 151 (invited contribution).
E. Shane Price, Matthew S. DeVore, and Carey K. Johnson, Detecting Intramolecular Dynamics and Multiple FRET States by Fluorescence Correlation Spectroscopy, J. Phys. Chem. B. 114, 5895–5902 (2010).
Krzysztof Kuczera, Jay Unruh, Carey K. Johnson, and Gouri S. Jas, Reorientations of Aromatic Amino Acids and Their Side Chains Models: Anisotropy Measurements and Molecular Dynamics Simulations, J. Phys. Chem. A, 114, 133–142 (2010).
Jay R. Unruh, Krzysztof Kuczera, and Carey K. Johnson, Conformational Heterogeneity of a Leucine Enkephalin Analog in Aqueous Solution and SDS Micelles: Comparison of Time-Resolved FRET and Molecular Dynamics Simulations, J. Phys. Chem. B 113, 14381-14392 (2009).
Peter Adany, E. Shane Price, Carey K. Johnson, Run Zhang and Rongqing Hui, Switching of 800 nm Femtosecond Laser Pulses Using a Compact PMN-PT Modulator, Rev. Sci. Instrum. 80, 033107-1-5 (2009).
Mangala Roshan Liyanage, Asma Zaidi, and Carey K. Johnson, Fluorescence Polarization Assay for Calmodulin Binding to Plasma Membrane Ca2+–ATPase: Dependence on Enzyme and Ca2+ Concentrations, Anal. Biochem. 385, 1-6 (2009).
Carey K. Johnson, “Fluorescence Techniques for Proteins,” in Wiley Encyclopedia of Chemical Biology, ed. T.P. Begley, (Wiley, 2008).
Abhijit Mandal, Mangala Roshan Liyanage, Asma Zaidi, and Carey K. Johnson, Interchange of Autoinhibitory Domain Conformations in Plasma-Membrane Ca2+-ATPase-Calmodulin Complexes, Protein Science 17, 555-562 (2008).
Timothy S. Priddy, E. Shane Price, Carey K. Johnson, and Gerald M. Carlson, Single Molecule Analyses of the Conformational Substates of Calmodulin Bound to the Phosphorylase Kinase Complex, Protein Science 16, 1017-1023 (2007).
Jay R. Unruh, Mangala Roshan Liyanage, and Carey K. Johnson, Tyrosyl Rotamer Interconversion Rates and the Fluorescence Decays of N-Acetyltyrosinamide and Short Tyrosyl Peptides, J. Phys. Chem. B 111, 5494-5502 (2007).
Brian D. Slaughter, Ramona J. Bieber Urbauer, Jeffrey L. Urbauer, and Carey K. Johnson, Mechanism of Calmodulin Recognition of the Binding Domain of Isoform 1b of the Plasma Membrane Ca2+-ATPase: Kinetic Pathway and Effects of Methionine Oxidation, Biochemistry 46, 4045-4054 (2007).