The Kollman Lab studies the intracellular organization of bacterial cells. Historically, bacteria have been viewed as simple organisms with very little internal organization, often described as mere ‘bags of enzymes’. But recent work has shown that bacteria, like their eukaryotic cousins, make use of cytoskeletal systems and organelles to organize their internal space. Our work is focused on understanding the structures of the macromolecular machines that drive the organizing processes.
Our structural approach centers on cryo-electron micrsocopy (cryo-EM), which allows us to determine three-dimensional structures of isolated protein complexes at high resolution, and to examine those structures in their native cellular environment. We use complementary techniques like x-ray crystallography to access higher resolution information, and are using correlative approaches to combine fluorescence microscopy and cryo-EM of the same cellular samples. By integrating all of these approaches, we aim to generate mechanistic insights over a broad range of size and resolution scales.
One area of current research in our lab is investigating the mechanisms of plasmid segregation by bacterial actin-like proteins. Some large, low-copy number plasmids, including many virulence plasmids, require active segregation systems to ensure each daughter cell receives a plasmid copy at cell division. We are combining structural studies of the components of the segregation machinery – both in isolation and in their native cellular environment – with biochemical characterization of the interactions between the components. Detailed mechanistic understanding of segregation in these systems will not only shed light on unique aspects of bacterial cell biology, but may provide new approaches for the targeted disruption maintenance of virulence plasmids.
We also study the assembly of magnetosomes, unique membrane-bound bacterial organelles that serve as sites for biomineralization of tiny magnetic crystals, which allow bacteria to orient themselves in the earth’s magnetic field. We aim to generate a complete molecular model of the magnetosome by combining structures of the intact organelle with higher resolution structures of individual components. This unique system is an attractive model for understanding basic principles of organelle biogenesis and processes of biomineralization; moreover, a number of practical applications are being developed in which functionalized magnetosome membranes can be directed to targets by taking advantage of their magnetic properties.
Positions are available for highly motivated graduate students and postdocs. Please send inquiries directly to Dr. Kollman (justin [dot] kollman [at] mcgill [dot] ca (justin [dot] kollman [at] mcgill [dot] ca))
Kollman, JM, Merdes, A, Mourey L, Agard, DA (2011) Microtubule nucleation by g-tubulin complexes. Nat. Rev. Mol. Cell Biol. 12, 709-721.
Guillet V, Knibiehler M, Gregory-Pauron L, Remy M-H, Cemin C, Raynaud-Messina B, Bon C, Kollman JM, Agard DA, Mourey L, Merdes A (2011) Insight into g-tubulin complex assembly from the crystal structure of GCP4. Nat. Struct. Mol. Biol. 18, 915-919.
Rivera, CR, Kollman, JM, Polka, JK, Agard, DA, Mullins, RD. (2011) Architecture and assembly of a divergent member of the ParM family of bacterial actin like proteins. J. Biol. Chem. 286, 14282-14290.
Kollman, JM, Polka, JK, Zelter, A, Davis, TN, Agard, DA. (2010) Microtubule nucleating g-TuSC assembles structures with 13-fold microtubule-like symmetry. Nature 466, 879-882.
Choy, RM, Kollman, JM, Zelter, A, Davis, TN, Agard, DA. (2009) Localization and orientation of the g-Tubulin Small Complex components using protein tags as labels for single particle EM. J. Struct. Biol. 168, 571-574.
Polka, JK, Kollman, JM, Agard, DA, Mullins RD. (2009) The Structure and Assembly Dynamics of Plasmid Actin AlfA Imply a Novel Mechanism of DNA Segregation. J. Bacteriol. 191, 6219-6230.
Pandi L, Kollman JM, Lopez-Lira F, Burrows J, Riley M, Doolittle RF. (2009) Two Families of Synthetic Peptides That Enhance Fibrin Turbidity and Delay Fibrinolysis by Different Mechanisms. Biochemistry 48, 7201-7208.
Kollman JM, Pandi L, Sawaya MR, Riley M, Doolittle RF. (2009) Crystal Structure of Human Fibrinogen. Biochemistry 48, 3877-3886.
Kollman JM, Zelter A, Muller EG, Fox B, Davis TN, Rice LM, Agard DA. (2008) The structure of the gamma-tubulin small complex: implications of its architecture and flexibility for microtubule nucleation. Mol. Biol. Cell 19, 207-215.
Zheng SQ, Kollman JM, Braunfeld MB, Sedat JW, Agard DA. (2006) Automated acquisition of electron microscopic random conical tilt sets. J. Struct. Biol. 157, 148-155.
Doolittle RF, Kollman JM. (2006) Natively unfolded regions of the vertebrate fibrinogen molecule. Proteins 63, 391-397.
Kollman JM, Quispe J. (2005) The 17 Å structure of the 420 kDa lobster clottable protein by single particle reconstruction from cryoelectron micrographs. J. Struct. Biol. 151, 306-314.
Kollman JM, Doolittle RF. (2005) Unusual noncrystallographic symmetry in crystals of a 420 kDa crustacean clottable protein. Acta Cryst. D61, 485-489.
Yang Z, Kollman JM, Pandi L, Doolittle RF. (2001) Crystal structure of native chicken fibrinogen at 2.7 Å resolution. Biochemistry 40, 12515-23.
Kollman JM, Doolittle RF. (2000) Determining the relative rates of change for prokaryotic and eukaryotic proteins with anciently duplicated paralogs. J. Mol. Evol. 51, 173-81.
Tseng TT, Gratwick KS, Kollman J, Park D, Nies DH, Goffeau A, Saier MH Jr. (1999) The RND permease superfamily: an ancient, ubiquitous and diverse family that includes human disease and development proteins. J. Mol. Microbiol. Biotechnol. 1, 107-25.
Saier MH Jr, Kollman JM. (1999) Is FatP a long-chain fatty acid transporter? Mol. Microbiol. 33, 670-2.