Melanie Ohi
Faculty Member
Last active: 2/4/2016

Profile

Proteins carry out most cellular processes as members of dynamic multi-protein assemblies. Although progress has been made cataloging the constituents of specific complexes, we have only limited knowledge of how proteins assemble into macromolecular machines and how these machines perform their cellular functions. We are using yeast genetics, biochemistry and single particle cryo-electron microscopy (EM) to explore the structural and functional organization of complexes involved in pre-mRNA splicing and complexes involved in the protein ubiquitination pathway.

Single Particle Cryo-Electron Microscopy
Single particle cryo-EM is a powerful technique for determining the structures of large, dynamic complexes that are too difficult to crystallize. In this structural approach, purified complexes are applied to grids covered with holey carbon film and quickly frozen by plunging the grids into liquid ethane. The rapid freezing prevents water from forming ice crystals and embeds the molecules in a layer of vitrified (or amorphous) ice preserving the specimen in a near-native environment. Images of the preserved particles are taken using an electron microscope. Digital image processing methods are then used to produce 3D models from the images of complex particles trapped in vitrified ice.

The Spliceosome
Although the human genome contains ~25,000 genes, it is estimated that we make over 90,000 proteins. The disparity between our genome and our proteome can be explained by the activity of the spliceosome, a large macromolecular machine composed of RNA and protein components. This complex catalyzes the excision of non-coding introns from a pre-messenger RNA (pre-mRNA) to create a mature message (mRNA). Although the composition of the spliceosome is known, it remains a mystery how this dynamic machine functions. To understand spliceosome function and regulation it will be essential to develop three-dimensional (3D) pictures of how the numerous spliceosomal proteins and RNA components organize into one machine. A number of projects in the lab focus on the functional and structural characterization of stable spliceosomal complexes isolated from the fission yeast S. pombe.

Pore Forming Toxins
There are a number of projects in the lab that focus on studying the structure and function of pore forming bacterial toxins. We work with a multidisciplinary team of researchers to understand how these toxins function as both soluble and membrane inserted proteins, with the main goal of gaining a mechanistic understanding of how these toxins contribute to pathogenesis.

Publications

The following timeline graph is generated from all co-authored publications.

Featured publications are shown below:

  1. The Tubulation Activity of a Fission Yeast F-BAR Protein Is Dispensable for Its Function in Cytokinesis. McDonald NA, Takizawa Y, Feoktistova A, Xu P, Ohi MD, Vander Kooi CW, Gould KL (2016) Cell Rep 14(3): 534-46
    › Primary publication · 26776521 (PubMed) · PMC4731314 (PubMed Central)
  2. Molecular and Structural Analysis of the Helicobacter pylori cag Type IV Secretion System Core Complex. Frick-Cheng AE, Pyburn TM, Voss BJ, McDonald WH, Ohi MD, Cover TL (2016) MBio 7(1): e02001-15
    › Primary publication · 26758182 (PubMed) · PMC4725015 (PubMed Central)
  3. Oligomerization but Not Membrane Bending Underlies the Function of Certain F-BAR Proteins in Cell Motility and Cytokinesis. McDonald NA, Vander Kooi CW, Ohi MD, Gould KL (2015) Dev Cell 35(6): 725-36
    › Primary publication · 26702831 (PubMed) · PMC4691284 (PubMed Central)
  4. Cryo-electron microscopy and the amazing race to atomic resolution. Binshtein E, Ohi MD (2015) Biochemistry 54(20): 3133-41
    › Primary publication · 25955078 (PubMed)
  5. Kinesin-12 Kif15 targets kinetochore fibers through an intrinsic two-step mechanism. Sturgill EG, Das DK, Takizawa Y, Shin Y, Collier SE, Ohi MD, Hwang W, Lang MJ, Ohi R (2014) Curr Biol 24(19): 2307-13
    › Primary publication · 25264249 (PubMed) · PMC4207087 (PubMed Central)
  6. Structural and functional insights into the N-terminus of Schizosaccharomyces pombe Cdc5. Collier SE, Voehler M, Peng D, Ohi R, Gould KL, Reiter NJ, Ohi MD (2014) Biochemistry 53(41): 6439-51
    › Primary publication · 25263959 (PubMed) · PMC4204884 (PubMed Central)
  7. Gle1 functions during mRNA export in an oligomeric complex that is altered in human disease. Folkmann AW, Collier SE, Zhan X, Aditi , Ohi MD, Wente SR (2013) Cell 155(3): 582-93
    › Primary publication · 24243016 (PubMed) · PMC3855398 (PubMed Central)
  8. Structural and functional characterization of the N terminus of Schizosaccharomyces pombe Cwf10. Livesay SB, Collier SE, Bitton DA, Bähler J, Ohi MD (2013) Eukaryot Cell 12(11): 1472-89
    › Primary publication · 24014766 (PubMed) · PMC3837936 (PubMed Central)
  9. Molecular assembly of botulinum neurotoxin progenitor complexes. Benefield DA, Dessain SK, Shine N, Ohi MD, Lacy DB (2013) Proc Natl Acad Sci U S A 110(14): 5630-5
    › Primary publication · 23509303 (PubMed) · PMC3619295 (PubMed Central)
  10. Nature of KaiB-KaiC binding in the cyanobacterial circadian oscillator. Pattanayek R, Yadagiri KK, Ohi MD, Egli M (2013) Cell Cycle 12(5): 810-7
    › Primary publication · 23388462 (PubMed) · PMC3610728 (PubMed Central)
  11. Structural analysis of the oligomeric states of Helicobacter pylori VacA toxin. Chambers MG, Pyburn TM, González-Rivera C, Collier SE, Eli I, Yip CK, Takizawa Y, Lacy DB, Cover TL, Ohi MD (2013) J Mol Biol 425(3): 524-35
    › Primary publication · 23178866 (PubMed) · PMC3612943 (PubMed Central)
  12. The human metapneumovirus fusion protein mediates entry via an interaction with RGD-binding integrins. Cox RG, Livesay SB, Johnson M, Ohi MD, Williams JV (2012) J Virol 86(22): 12148-60
    › Primary publication · 22933271 (PubMed) · PMC3486500 (PubMed Central)
  13. Tailoring of membrane proteins by alternative splicing of pre-mRNA. Mittendorf KF, Deatherage CL, Ohi MD, Sanders CR (2012) Biochemistry 51(28): 5541-56
    › Primary publication · 22708632 (PubMed) · PMC3448030 (PubMed Central)