3258 TAMU
College Station, TX 77843-3258

Office:
Biological Sciences Building West
Room 119C
979-845-1164

Lab:
Microscopy Imaging Center

Fax: 979-845-2891
Email: holzen@mic.tamu.edu

Andreas Holzenburg has employed electron microscopy (EM)/crystallography as a tool for the structural elucidation of (sub)cellular components and biological macromolecules, particularly transmembrane and membrane-associated proteins. The structure determination involves image processing routines and is carried out in conjunction with thorough biochemical characterisations with the view to establish structure-function relationships. Furthermore, the EM approach is often used jointly with other biophysical approaches including X-ray crystallography and spectroscopical methods. As EM is an extremely versatile tool, a number of collaborations on structure-oriented projects have been supported (see publications).

Structure and Function of the Plastid Division Machinery
The Holzenburg lab is interested in the structure, assembly and turnover dynamics of the cytoskeletal tubulin-like FtsZ protein in plant chloroplats. FtsZ plays a pivotal role in the division of prokaryotic cells as well as chloroplasts. One of the functional characteristics of FtsZ is its auto-assembly into a ring-like macromolecular complex called the Z-ring. During cell division, the Z-ring undergoes continuous and rapid remodeling via subunit exchange and constricts at the leading edge of the septum with the simultaneous loss of subunits. Consistent with the endosymbiotic origin of chloroplasts, plants possess nuclear-encoded, plastid-targeted homologues of bacterial FtsZ. However, whereas most prokaryotes, including the cyanobacterial relatives of chloroplasts, have a single form of FtsZ, two structurally distinct FtsZ protein families, FtsZ1 and FtsZ2. Experimental evidence suggests that FtsZ1 and FtsZ2 function in a complex and that their roles are functionally distinct. They are both localized in the stromal compartment of the chloroplast and are always tightly colocalized in immuno-fluorescence labeling experiments. In addition, FtsZ1 seems unable to form long polymers in planta without FtsZ2.

Overall, the molecular mechanism of FtsZ filament assembly and its regulation, the structures of assembled protofilaments, and the structure of the in vivo FtsZ ring in chloroplasts remain poorly understood. Our overall goal is to expand the current model for FtsZ assembly and investigate and define the molecular structure and assembly dynamics of FtsZ rings in chloroplasts of Arabidopsis thaliana with the view to understand chloroplast size control.

Modulation of the size of storage plastids (amyloplasts) and the starch granule size by changing the levels of FtsZ expression is of considerable interest to the starch and biofuel industry, since increased starch granule size improves the wet-milling efficiency and thus the starch yield in staple crops.

Ford, R.C. and Holzenburg, A.: Electron crystallography of biomolecules: mysterious membranes and missing cones. Trends Biochem. Sci. 33, 38-43 (2008).

Smith A.G., Johnson, C.B., Ellis, E.A., Vitha, S. and Holzenburg, A: Protein screening using cold microwave technology. Anal. Biochem. 375, 313-317 (2008).

Sun, J., Dufort, C., Daniel, M.C., Murali, A., Chen, C., Gopinath, K., Stein, B., De, M., Rotello, V.M., Holzenburg, A., Kao, C.C. and Dragnea, B.: Core-controlled polymorphism in virus-like particles. Proc. Natl. Acad. Sci. U.S.A. 104, 1354-1359 (2007).

Ramesh, A., Savva, C.G., Holzenburg, A. and Sacchettini, J.C.: Crystal structure of Rsr, an ortholog of the antigenic Ro protein, links conformational flexibility to RNA binding activity. J. Biol. Chem. 282,14960-14967 (2007).

Ranjith-Kumar, C.T., Miller, W., Sun, J., Xiong, J., Santos, J., Yarbrough, I., Lamb, R.J., Mills, J., Duffy, K.E., Hoose, S., Cunningham, M., Holzenburg, A., Mbow, M.L., Sarisky, R.T. and Kao, C.C.: Effects of single nucleotide polymorphisms on Toll-like receptor 3 activity and expression in cultured cells. J. Biol. Chem. 282, 17696-17705 (2007).

Heuck, A.P., Savva, C.G., Holzenburg, A. and Johnson, A.E.: Conformational changes that effect oligomerization and initiate pore formation are triggered throughout perfringolysin O upon binding to cholesterol. J. Biol. Chem. 282, 22629-22637 (2007).

Hawkins, D.M., Ellis, E.A., Stevenson, D., Holzenburg, A. and Reddy, S.M.: Novel critical point drying (CPD) based preparation and transmission electron microscopy (TEM) imaging of protein specific molecularly imprinted polymers (HydroMIPs). J. Mater. Sci. 42, 9465-9468 (2007).

Sun, J., Duffy, K.E., Ranjith-Kumar, C.T., Xiong, J., Lamb, R.J., Santos, J., Masarapu, H., Cunningham, M., Holzenburg, A., Sarisky, R.T., Mbow, M.L. and Kao, C.: Structural and functional analyses of the human Toll-like receptor 3. Role of glycosylation. J. Biol. Chem. 281, 11144-11151 (2006).

Bhardwaj, K., Sun, J., Holzenburg, A., Guarino, L.A. and Kao, C.: RNA recognition and cleavage by the SARS coronavirus endoribonuclease. J. Mol. Biol. 361, 243-256 (2006).

Hawkins, D.M., Trache A., Ellis, E.A., Stevenson D., Holzenburg, A., Meininger, G.A. and Reddy, S.M.: Quantification and confocal imaging of protein specific molecularly imprinted polymers. Biomacromolecules 7, 2560-2564 (2006).

Weiss, J.L., Evans, N.A., Ahmed, T., Wrigley, J.D.J., Khan, S., Wright,C., Keen, J.N., Holzenburg, A. and Findlay, J.B.C.: Methionine-rich repeat proteins: a family of membrane-associated proteins which contain unusual repeat regions. Biochim. Biophys. Acta 1668, 164-174 (2005).

Sun, J., Savva, C.G., Deaton, J., Kaback, R.H., Svrakic, M., Young, R. and Holzenburg, A.: Asymmetric binding of membrane proteins to GroEL. Arch. Biochem. Biophys. 434, 352-357 (2005).

Colangeli, R., Helb, D., Sridharan, S., Sun, J., Varma-Basil, M., Hazbón, M.H., Harbacheuski, R., Megjugorac, N.J., Jacobs Jr, W.R., Holzenburg, A., Sacchettini, J.C. and Alland, D.: The Mycobacterium tuberculosis iniA gene is essential for activity of an efflux pump that confers drug tolerance to both isoniazid and ethambutol. Mol. Microbiol. 55, 1829-1840 (2005).

Guarino, L.A., Bhardwaj, K., Dong.,W., Sun, J., Holzenburg, A. and Kao, C.: Mutational analysis of the SARS virus Nsp15 endoribonuclease: identification of residues affecting hexamer formation. J. Mol. Biol. 353, 1106-1117 (2005).

Holzenburg, A., H. Xue, H. Zheng, H.M. Li, A. Kitmitto, H. Zhu, and P. Lee. 2000. A fragment of recombinant GABAA receptor alpha1 subunit forming rosette-like homo-oligomers. J. Mol. Biol. 296, 739-742.

Holzenburg, A., I. Simidjiev, S. Stoylova, H. Amenitsch, T. Javorfi, L. Mustardy, P. Laggner, and G. Garab. 2000. Self-assembly of large-ordered lamellae from non-bilayer lipids and integral membrane proteins in vitro. Proc. Natl. Acad. U.S.A 97, 1473-1476.

Holzenburg, A., S.S. Stoylova, P.J. Lenting, G. Kemball-Cook. 1999. Electron crystallography of human blood coagulation factor VIII bound to phospholipid monolayers. J. Biol. Chem. 274, 36573-36578.

Holzenburg, A., A. Pilling, M.F. Rosenberg, S.H. Willis, J. Jäger, G.H. Cohen, R.J. Eisenberg, and D.M Meredith. 1999. The three-dimensional structure of herpes simplex virus type 1 glycoprotein D at 2.4 nm resolution. J. Virology 73, 7830-7834.

Holzenburg. A., S.S. Stoylova, and R.C. Ford. 1999. Cryo-electron crystallography of small and mosaic 2-D crystals: An assessment of a procedure for high-resolution data retrieval. Ultramicroscopy 77, 113-128.

Holzenburg, A., A. Kitmitto, A.O. Mustafa, and R.C. Ford. 1998. Three-dimensional structure of higher plant photosystem I determined by electron crystallography. J. Biol. Chem. 273, 29592-29599.