University of Toronto Biochemistry

	Trevor F. Moraes Assistant Professor B.Sc., Queen's University, 1997 M.Sc., Queen's University, 1999 Ph.D., University of Alberta, 2004 PDF, University of British Columbia
	Medical Sciences Building, Room 5366 416-946-3048 trevor.moraes@utoronto.ca

Structure and Function of Ion and Protein Translocation Machineries

Go to Moraes Lab Homepage

Research Synopsis

Proteins and small molecules are translocated across lipid bilayers by integral membrane proteins that span the bilayer and facilitate translocation. My lab centers around determining the atomic resolution structure of membrane proteins and complexes that function to transport materials across lipid bilayers. The primary focus of research in the lab will be on ion transport, with an initial emphasis on phosphate and iron uptake mechanisms within pathogenic bacterial species including the Pseudomonadaceae and Neisseriaceae families. In addition to the structural and biochemical characterization of these ion transport system components, we will examine the membrane protein complexes that facilitate the proper insertion and assembly of these membrane protein transport components.

Phosphate specific transport and the Pho Regulon within Pseudomonas aeruginosa : Phosphate plays an essential role in metabolic, catabolic, and signaling events within virtually all living organisms. As such, the trafficking of phosphate anions is an immensely important function, yet the specific mechanism utilized to transport inorganic phosphate molecules across a lipid bilayer remains unclear. The Gram negative bacterial cell utilizes a double membrane system and employs a plethora of channels that can be constitutive or specifically expressed in its outer membrane ( OM ) in response to various environmental conditions. Most bacteria, including Pseudomonas react to environmental conditions of low phosphate by turning on a gene regulon leading to the expression of a number of phosphate trafficking proteins. This regulation is mediated by regulatory proteins anchored in the inner membrane (PhoR), which sense phosphate levels through an as yet uncharacterized interaction with the inner membrane transport complex.

Amongst these up-regulated proteins are structural proteins designed to scavenge phosphate from the surrounding environment including: OprP (a phosphate specific outer membrane transporter), PhoS (a phosphate specific periplasmic binding protein) and PhoABC (a phosphate specific inner membrane ABC importer). We have begun to structurally characterize all of the components of this transport pathway and delineate the mechanism of transport in molecular detail through a combination of crystallography, site-directed mutagenesis, and biochemical and functional characterization.

Iron acquisition through the bacterial transferrin receptor: In the vertebrate host, the level of free extracellular iron is well below that required to support the growth of bacterial pathogens, largely owing to the iron-sequestering effects of the iron-binding glycoproteins transferrin and lactoferrin. Successful bacterial pathogens have developed high-affinity iron uptake systems capable of acquiring iron from transferrin and lactoferrin. Members of the Neisseriacea and Pasteurellaceae family including Neisseria meningitidis and Haemophilus influenza possess receptors consisting of the surface exposed lipoprotein TbpB and the integral outer membrane protein TbpA that bind transferrin and are involved in the retrieval and transport of iron across the outer membrane. Within the periplasm, the ferric binding protein, FbpA, binds iron and escorts it to the inner membrane ABC transporter where it is transported into the cytoplasm.

The structural information gained about the conserved interactions between these essential outer membrane proteins and transferrin will represent the target regions for the development of broad-spectrum vaccines against these highly infectious bacterial pathogens.

Selected Publications

Calmettes C, Alcantara J, Yu RH, Schryvers AB, and Moraes T.F. The structural basis of transferrin sequestration by transferrin-binding protein B. Nature Structural and Molecular Biology 2012 Feb 19. doi: 10.1038/nsmb.2251. [Epub ahead of print]

Calmettes C, Yu RH, Silva LP, Curran D, Schriemer DC, Schryvers AB, and Moraes T.F. Structural variations within the transferrin binding site on transferrin binding protein B, TbpB.. J Biol Chem. 2011 Feb 5. [Epub ahead of print].

Babu M, Greenblatt JF, Emili A, Strynadka NC, Reithmeier RA and Moraes T.F. Structure of a SLC26 anion transporter STAS domain in complex with acyl carrier protein: implications for E. coli YchM in fatty acid metabolism. Structure. 2010; 18(11):1450-62.

Moraes T.F., Yu RH, Strynadka NC, Schryvers AB. Insights into the bacterial transferrin receptor: the structure of transferrin-binding protein B from Actinobacillus pleuropneumoniae. Molecular Cell. 2009; 35(4):523-33.

Okon M., Moraes T.F., Lario P.I., Creagh L., McIntosh L. and Strynadka N.C.J. Structural characterization of the type III pilot-secretin complex from Shigella flexneri . Structure . 2008 Oct 8;16(10):1544-54.

Moraes T.F., Spreter T. and Strynadka N.C.J. Piecing together the Type III Injectisome of Bacterial Pathogens. Current Opinions in Structural Biology: Macromolecular Assemblies . 2008; 18(2). 258-266.

Moraes T.F. , Bains M., Hancock R.E.W., Strynadka N.C.J. An arginine ladder in OprP mediates phosphate-specific transfer across the outer membrane. Nature Structural and Molecular Biology 2007;14, 85-87.

Moraes T.F. , Edwards R.A., McKenna S., Pastushok L., Xiao, W., Glover J.N.M. and Ellison M.J. (2001) Crystal structure of the human ubiquitin conjugating enzyme complex, hMms2-hUbc13. Nature Structural Biology, 8:669-673.

Department of Biochemistry
University of Toronto
Toronto, Canada

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