Biology

Ingeborg Schmidt-Krey, Assistant Professor: Biology

Ph.D., Biophysics and Structural Biology, Karolinska Institute, 1999

Phone: 404-385-0286
Fax: 404-894-0519
Office: (Cherry Emerson) A118

Research Interests

Structure and function of eukaryotic membrane proteins; two-dimensional crystallization; electron crystallography; electron cryo-microscopy (cryo-EM)

Overview

Eukaryotic membrane proteins comprise approximately 60% of all drug targets and are consequently immensely important for biomedical research. Despite their importance, only few could thus far be studied at the structural level. My research focuses on the crystallization, structure and function of eukaryotic membrane proteins.

Electron crystallography is the main tool employed to study these proteins in my laboratory. Initially, this involves testing of conditions for growing two-dimensional (2D) crystals, usually by reconstituting the detergent-solubilized membrane protein into a bilayer. Once crystallization parameters have been identified by electron microscopy of negatively stained samples, electron cryo-microscopy is employed to collect high-resolution data. The structure is then obtained by image processing.

The approach of 2D crystallization and electron crystallography is particularly suitable for highly fragile membrane proteins such as many eukaryotic ones. An advantage compared to three-dimensional crystals is that only small amounts of protein are required. Reconstitution ensures an environment that is close to the native one, the detergent is removed, and functional studies are relatively easily undertaken. Experimental phases are obtained due to the fact that images are collected. In some instances the image amplitudes can be substituted with electron diffraction amplitudes.

In a collaboration with Drs. Yoshihide Kanaoka, Bing K. Lam, and K. Frank Austen in the Department of Medicine at Harvard Medical School we would like to understand membrane proteins involved in the synthesis and signaling of lipid mediators. We aim to go beyond determining the structure and reveal the distinct reaction mechanism. Human leukotriene C4 synthase (LTC4S) plays a significant role in asthma and has yielded well-ordered two-dimensional crystals and initial structural information.

Another collaboration with Dr. Darrel W. Stafford in the Department of Biology and Center for Thrombosis and Hemostasis at the University of North Carolina at Chapel Hill seeks to understand membrane proteins important in blood coagulation, such as the human vitamin K-dependent g-glutamyl carboxylase.

Although electron crystallographic methods are well developed, little is known about the factors important in 2D crystallization, and screening protocols as for 3D crystallization do not exist. An important sideline of my research interests aims at developing screening methods and strategies for 2D crystallization and understanding the underlying mechanisms.

Selected Publications

Schmidt-Krey, I., Kanaoka, Y., Mills, D.J., Irikura, D., Haase, W., Lam, B.K., Austen, K.F. and Kühlbrandt, W. (2004) Human leukotriene C4 synthase at 4.5 Å resolution in projection. Structure, 12, 2009-2014.

Schmidt-Krey, I. (2005) Electron crystallography of membrane proteins: Two-dimensional crystallization and screening by electron microscopy. Methods, Invited article.

Schmidt-Krey, I., Mutucumarana, V., Haase, W., Stafford, D.W. and Kühlbrandt, W. (2006) Two-dimensional crystallization of human vitamin K-dependent g-glutamyl carboxylase. J. Struct. Biol. http://dx.doi.org/10.1016/j.jsb.2006.08.002