Startsida
Annica Theresia Johnsson
Molecular Biotechnology, IFM
Annica Theresia Johnsson, MSc
Division of Molecular Biotechnology
Department of Physics, Chemistry and Biology
Linköping University
SE-581 83 Linköping
Office: +46 (0)13 286614
E-mail: annij@ifm.liu.se
Research
Biophysical characterization of proteins using nuclear magnetic resonance spectroscopy
The main focus of my research is biophysical characterization of proteins using nuclear magnetic resonance (NMR) spectroscopy. This is an incredibly useful and powerful technique when it comes to studying proteins and their properties since it is possible to study them at atomic resolution. NMR spectroscopy has an enormously wide range of applications for biomolecules. For instance, it is possible to determine the structure of a protein, study its dynamical properties on various time scales, investigate solvent accessibility, interactions with ligands and other proteins, relative orientations of protein domains, pH and temperature dependence, effects of co-solvent and more. But perhaps the most interesting feature of NMR is the possibility to detect and characterize intermediate protein states that are invisible to most other types of spectroscopy. In my research, I try to explore and utilize the many possibilities of this versatile technique.
Current projects
The TPMT project
The protein thiopurine methyl S-transferase (TPMT) is a cytosolic protein that catalyses the transfer of methyl groups to pharmaceutical substances used as cytostatics and immunosuppressors in several medical conditions. This activity is not at all desired since the drugs lose their efficacy. Several different variants of this protein exist in a given population, all with their distinct activity towards the pharmaceuticals. As a consequence, the precise genotype of a patient has to be determined before administration to avoid drug induced toxicity.
This research project is a collaboration with Lars-Göran Mårtensson and Patricia Wennerstrand at Linköping University. We use NMR spectroscopy to investigate the biophysical and structural properties of different TPMT protein variants to explore the reasons for their diverse activities towards certain pharmaceutical drugs.
The PDZ project
The PDZ protein domain occurs frequently as a constituent part of multidomain proteins, where it usually functions as a protein-protein interaction domain. This project is a collaboration with Per Jemth's research group at Uppsala University. We aim to study the folding intermediate of a PDZ domain from the multidomain protein SAP97 using NMR spectroscopy. This particular protein and its PDZ domains are the target for the E6 protein of the human papilloma virus. Once the virus has infected a human cell, the E6 viral protein binds to the PDZ domains of SAP97. Binding of E6 targets the SAP97 protein for proteasomal degradation. This in turn causes the cell to proliferate and become immortal.
The R1ρ project
Protein dynamics are vital for life processes as the ability of a protein to alter its conformation may be crucial for its function. The microsecond to millisecond time scale is particularly interesting in this respect, since biologically relevant processes, ranging from catalysis, ligand binding and folding, to interactions and signal propagation, occur within this time frame. Protein dynamics on this time scale can be studied with NMR spectroscopy by using R1ρ experiments. In this project, initiated by the former Forum member Janosch Hennig, we have developed an R1ρ experiment to measure µs-ms dynamics on protein methyl protons.
Protein purification
Since solution state NMR requires large amounts of protein, a frequently reoccurring part of my research is to express and purify the proteins I work with. To obtain as much protein as I can, I strive to improve and optimize my existing purification protocols to find time efficient, easy-to-use solutions that minimize protein loss during purification. Also, I try to increase recombinant protein expression by modifying growth conditions when needed.
Supervisors
Nalle Johnsson, Professor (IFM Molecular Biotechnology)
Patrik Lundström, Assistant Professor (IFM Molecular Biotechnology)
Page responsible:
jonathan.rakar@liu.se
Last updated: Thu Feb 09 11:09:30 CET 2012
