Molecular interactions form the basis for all cellular functions ranging from nutrient sequestration to signal transduction. While specific interactions have been extensively studied in the biomolecular context, the importance of non-specific and weak interactions between proteins have also become apparent. In this dissertation I study two phenomena that are emergent from non-specific and weak interactions: the effect of macromolecular crowding on protein-ligand equilibria and the regulatory effects of macromolecules on liquid-liquid phase separation of proteins. In the first project, I have shown that macromolecular crowders can compete with ligands for ligand binding proteins and are just as sensitive to conformational changes in the protein as ligands are. More specifically I showed, the polymeric crowder Ficoll70 competes against maltose for maltose binding protein (MBP) for the same binding site. I also showed the protein crowder BSA shows similar competitive effects. In the second project, I have experimentally verified the existence of three archetypical classes of regulators that can affect the liquid-liquid phase boundary of proteins that form membraneless organelles inside the cell. The three classes were passive promotors, active suppressors and active promotors, exemplified by the polymeric crowder Ficoll70, a positively charged folded protein lysozyme and a mimic of RNA, heparin. The third project continued from this and shows that intrinsically disordered proteins can dramatically alter liquid phase behavior of structured proteins. From these three studies I was able to show that bystander molecules in the cellular environment play a role in governing functional aspects of the cell. Two types of macromolecules, Ficoll70 and BSA, were shown to modulate MBP-maltose interactions. Three classes of macromolecules were shown to have disparate regulatory effects on the formation of membraneless organelles and some even form such organelles with distinct viscoelastic properties. / A Dissertation submitted to the Department of Molecular Biophysics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / 2019 / June 12, 2019. / Liquid-liquid phase separation, Macromolecular crowding, Membraneless organelles, Protein droplets / Includes bibliographical references. / Hong Li, Professor Co-Directing Dissertation; Huan-Xiang Zhou, Professor Co-Directing Dissertation; Jose Renato Dias Oliveira Pinto, University Representative; Prescott Bryant Chase, Committee Member; Michael Blaber, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_752350 |
| Contributors | Ghosh, Archishman (author), Li, Hong (professor co-directing dissertation), Zhou, Huan-Xiang (professor co-directing dissertation), Pinto, Jose R. (Jose Renato) (university representative), Chase, P. Bryant (committee member), Blaber, Michael (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Molecular Biophysics (degree granting departmentdgg) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, doctoral thesis |
| Format | 1 online resource (119 pages), computer, application/pdf |
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