| Author: | Kong, Wai Po |
| Title: | The dynamics of the full-length divsiome protein complex FTSQBL (FTSQ, FTSB AND FTSL) and its interaction with PBP1B of Escherichia coli |
| Advisors: | Wong, Kwok-yin (ABCT) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Escherichia coli Proteins Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Biology and Chemical Technology |
| Pages: | xi, 197 pages : color illustrations |
| Language: | English |
| Abstract: | Cell wall modification is a vital process in bacterial division, which is mainly regulated by a protein complex known as the “divisome”. This dedicated machinery contributes to cell wall invagination by synthesis and hydrolyzing septal peptidoglycan (sPG). Previous studies indicated that the E. coli divisome requires about ten essential proteins for proper function and cell separation. Among these, FtsQBL is a vital sub-complex controlling the sPG synthase PBP1b. Understanding the interaction between these proteins can provide insights into how the divisome works. Despite extensive efforts, the detailed interaction mechanism between the involved proteins: FtsQ, FtsB, FtsL and PBP1b, remains poorly understood. The fundamentals, structure and interaction information of FtsQ, FtsB, FtsL and PBP1b are given in Chapter 1. The Protein purification, protein structural model preparation and the corresponding characterization are discussed in Chapter 2. The interaction and conformational change upon the formation of the FtsQBL complex are discussed in Chapter 3. Hydrogen-deuterium-exchange mass spectrometry (HDX-MS) was used to investigate the full-length proteins and complexes of FtsQBL. The HDX data reveals that FtsB and FtsL interact at both the periplasmic and transmembrane regions to form a stable complex. Notably, part of the periplasmic region of FtsB undergoes significant conformational changes and transits from a flexible random structure into a helix. Molecular modeling suggests that the complexation of FtsB and FtsL brings the respective constriction control domains (CCDs) into close proximity. When adopting a coiled-coil structure, the CCDs maintain a fixed vertical distance relative to the membrane surface. Thus, this conformational change in forming the FtsBL complex may be essential for interacting with other divisomal proteins, such as FtsQ. In addition, molecular dynamics (MD) results indicate that the formation of the FtsQBL complex further refines the height of CCDs. Intriguingly, in the FtsQBL complex, only FtsB interacts with FtsQ at its C-terminal region, resulting in the stiffening of a large area of the β-domain in FtsQ. This leads to interlocks of the C-termini of FtsQBL into a sizeable domain. Furthermore, the hinge region between the α- and β-domains in FtsQ is rigidified in the FtsQBL complex. The interaction of FtsQBL with the sPG synthase PBP1b is reported in Chapter 4. HDX-MS study on the FtsQBL-PBP1b interaction reveals that the interaction with PBP1b is located at the amino acids near the CCD region of FtsL. This interaction also induces structural flexibility in both FtsB and FtsL. Interestingly, the presence of FtsQ prevents such destabilization in FtsBL without direct interaction with PBP1b. Both FtsBL and FtsQBL complexes influence the dynamics of PBP1b at the UB2H and glycosyltransferase (GT) domains. Unlike the small molecule inhibitor, MoeA, that directly blocks the GTase active site, the Fts-complexes restricted the flexibility of the enzymatic domain. Based on geometric considerations, this GTase inhibition by FtsBL and FtsQBL is probably achieved allosterically through interaction with the UB2H in PBP1b. On the other hand, the activator LpoB disrupts the local dynamics of PBP1b at the UB2H region without influencing the other two domains. This suggests that LpoB stimulates the PBP1b activity by destabilizing the UB2H and its interaction with the enzymatic domain. The HDX-MS results provide valuable insights into the structure, binding interface and regulatory mechanism of FtsQBL with PBP1b. |
| Rights: | All rights reserved |
| Access: | open access |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/13068