Department of Molecular Biology & Genetics

Sin Urban - Associate Professor, HHMI Molecular Biology & Genetics 725 N. Wolfe Street 507 PCTB Baltimore, MD 21205 Office: 410-502-6247 surban@jhmi.edu

Assistant:	Cynthia Rogers

Biochemistry, cell and chemical biology of intra-membrane proteases in cell signaling and microbial pathogenesis
Cell membranes are sites of interface between the cell and the outside world, and constitute major sites of signaling. Membranes also form the front lines where deadly pathogens first contact human cells and initiate infection. Our main focus is a family of membrane-immersed enzymes, termed rhomboid proteases, which catalyze a biochemical reaction that cuts protein segments within the membrane. This cleavage liberates proteins from the membrane, either to activate signals rapidly, or to inactivate other targets. Because of its speed and versatility, this basic biochemical reaction has evolved to control many cellular processes in all forms of life, from diverse bacteria to humans. But how these enzymes achieve catalysis within the membrane, and their roles in all but a few organisms, remain unclear. We study the biochemical principles governing how rhomboid enzymes catalyze reactions immersed within the membrane. We have reconstituted rhomboid activity with pure components, and are using a combination of membrane biochemistry, cell biology and chemical genetics to probe their mechanism. We have also focused on rhomboid function in deadly human pathogens, and discovered that rhomboid enzymes execute an array of essential functions: malaria and related parasites use their rhomboid enzymes to invade human cells, while a parasitic ameba uses its rhomboid in phagocytosis and immune evasion. Targeting rhomboid enzymes may be a way of treating multiple infectious diseases.

Relevant Publications:	Baker R.P. and S. Urban. Architectural and thermodynamic principles underlying intramembrane protease function. (2012). Nature Chemical Biology 8(9): 759-768. (DOI 10.1038/nchembio.1021) Link to Article Zhou Y., Moin S.M., Urban S. and Y. Zhang. An internal water-retention site in the rhomboid intramembrane protease GlpG ensures catalytic efficiency. (2012) Structure 20(7): 1255-1263. Link to Article Parussini F., Tang Q., Moin S.M., Mital J., Urban S. and G.E. Ward. Intramembrane proteolysis of Toxoplasma aplical membrane antigen 1 facilitates host-cell invasion but is dispensable for replication. (2012). Proc. Natl. Acad. Sci. USA 109 (19): 7463-7468. Link to Article Urban, S. and Dickey S.W. The rhomboid protease family; a decade of progress on function and mechanism. (2011). Genome Biology, 12(10): 231-41. Link to Article Urban, S. Making the cut: central roles of intramembrane proteolysis in pathogenic microorganisms (2009). Nature Reviews Microbiology 7: 411-423 [cover article] PubMed Abstract Baxt, L.A., Baker R.P., Singh U., and Urban, S. An Entamoeba histolytica rhomboid protease with atypical specificity cleaves a surface lectin involved in phagocytosis and immune evasion. (2008). Genes & Development 22(12): 1636-1646. [cover article] PubMed Abstract Urban, S. and R.P. Baker. In vivo analysis reveals substrate-gating mutants of a rhomboid intramembrane protease display increased activity in living cells. (2008). Biological Chemistry 389: 1107-1115. [cover article] PubMed Abstract Urban, S. and Y. Shi. Core principles of intramembrane proteolysis: comparison of rhomboid and site-2 family proteases. (2008). Current Opinion in Structural Biology 18(4): 432-441. PubMed Abstract Baker, R.P., Young K., Feng L., Shi Y. and Urban, S. Enzymatic analysis of a rhomboid intramembrane proteases implicates transmembrane helix 5 as the lateral substrate gate. (2007). Proc. Natl. Acad. Sci. USA. 104 (20): 8257-8262. [cover article] PubMed Abstract Wu Z., Yan N.,Feng L., Oberstein A., Yan H., Baker R. P., Gu L., Jeffrey P.D., Urban, S., and Y. Shi. Structural analysis of a rhomboid family intramembrane protease reveals a gating mechanism for substrate entry. (2006). Nature Structural and Molecular Biology. 13 (12): 1084-1091. PubMed Abstract Urban, S. Rhomboid proteins: conserved membrane proteases with divergent biological functions. (2006). Genes and Development. 20 (22): 3054-3068. PubMed Abstract Baker, R.P., Wijetilaka R, and Urban, S. Two Plasmodium rhomboid proteases preferentially cleave different adhesins implicated in all invasive stages of malaria. (2006). PLoS Pathogens. 10(2): e113. PubMed Abstract Brossier F., Jewett T., Sibley D. L., and Urban, S. A spatially-localized rhomboid protease cleaves cell surface adhesins essential for invasion by Toxoplasma. (2005). Proc. Natl. Acad. Sci. USA. <102(11):4146-4151. PubMed Abstract Urban, S. and M. S. Wolfe. Reconstitution of intramembrane proteolysis in vitro reveals that pure rhomboid is sufficient for catalysis and specificity. (2005). Proc. Natl. Acad. Sci. USA. 102(6):1883-1888. PubMed Abstract Urban, S. and M. Freeman. Substrate specificity of Rhomboid intramembrane proteases is governed by helix-breaking residues in the substrate transmembrane domain. (2003).Molecular Cell. 11: 1425-1434. PubMed Abstract Urban, S., Schlieper D., and M. Freeman. Conservation of intramembrane proteolytic activity and substrate specificity in prokaryotic and eukaryotic Rhomboids (2002).Current Biology. 12: 1507-1512. PubMed Abstract Urban, S., Lee J. R., and M. Freeman. A family of Rhomboid intramembrane proteases activates all Drosophila membrane-tethered EGF-like ligands (2002).EMBO Journal. 21: 4277-4286. PubMed Abstract Urban, S., Lee J. R., and M. Freeman. Drosophila Rhomboid-1 defines a family of putative intramembrane serine proteases. (2001). Cell. 107 (2): 173-182. PubMed Abstract

Graduate Program Affiliations	Biochemistry, Cellular & Molecular Biology (BCMB)