Award details

How are proteins targeted to curved membranes?

Reference	BB/I01327X/1
Principal Investigator / Supervisor	Professor Leendert Hamoen
Co-Investigators / Co-Supervisors
Institution	Newcastle University
Department	Inst for Cell and Molecular Biosciences
Funding type	Research
Value (£)	319,622
Status	Completed
Type	Research Grant
Start date	01/08/2011
End date	31/07/2014
Duration	36 months

Abstract

Many bacterial proteins have to localize at the cell division site or cell poles to function properly. A well known example is the conserved protein DivIVA. DivIVA functions as a scaffold for a wide variety of proteins that are involved in different cellular processes including cell division regulation, cell wall growth, and sporulation. Recently, we have shown that the strong membrane curvature that is generated during cell division functions as a cue for DivIVA targeting. How this protein recognizes the negatively curved (concave) cytoplasmic membrane at cell division sites is unclear. The aim of this project is to elucidate the mechanism responsible for binding of DivIVA to curved membranes. This has now become feasible thanks to the crystal structure of DivIVA that we have recently obtained. This structural information will enable us to: i) examine how DivIVA oligomers interact with the lipid membrane, ii) determine how the different domains of the molecule contribute to the recognition of negatively curved membranes, and iii) examine how DivIVA functions as a scaffold for other proteins. DivIVA is crucial for many morphogenetic processes and is essential for the viability of pathogens such as Mycobacterium tuberculosis and Streptococcus pneumoniae. Insight into the workings of this important morphogenetic protein will provide knowledge that will help us to better understand the physiology of these and other bacteria. While various recent studies have implicated membrane curvature as a topological marker for protein localization in the cell, the underlying mechanisms are still being debated. DivIVA is one of the very few model systems that have been used to study protein targeting to negatively curved membranes. The knowledge obtained with DivIVA will therefore be of general interest, including for those studying membrane curvature processes in eukaryotic cells.

Summary

Bacterial cells seem simple life forms, yet their internal cytoplasm is highly structured. Certain bacterial proteins require that they are positioned at the site where cell division takes place. DivIVA is a conserved protein that is involved in the targeting of a wide variety of proteins to the cell division site. The division of a bacterial cell is accomplished by the constriction of the cell membrane in the middle of the cell. During this process the cell membrane is strongly curved. Recently, we have shown that DivIVA is able to recognize and bind to these strongly curved membrane areas. How this occurs we do not know. The aim of this project is to discover what mechanism is responsible for the targeting of DivIVA to curved membranes. To achieve this we have to know in detail how this protein interacts with the cell membrane. This has become feasible thanks to the crystal structure of DivIVA that we have obtained. With this knowledge we can now: i) elucidate how DivIVA oligomers interact with the membrane, ii) determine how the different domains of the molecule contribute to recognition of curved membranes, and iii) how DivIVA functions as a scaffold for other proteins. This information will help us to build a model that can explain how proteins distinguish a curved cell membrane region from a flat cell membrane region. DivIVA is crucial for many morphogenetic processes and is essential for the viability of pathogens such as Mycobacterium tuberculosis and Streptococcus pneumoniae. Insight into the workings of this conserved protein will provide knowledge that will help us to better understand the physiology of these and other bacteria. While various recent studies have implicated membrane curvature as a topological marker for protein localization in the cell, the underlying mechanisms are still being debated. DivIVA is one of the very few model systems that have been used to study protein targeting to negatively curved (concave) membranes. The knowledge obtained with DivIVA will therefore be of general interest, including for those studying membrane curvature processes in complex eukaryotic cells.

Impact Summary

> Who will benefit? - The wider public - UK scientific competitiveness - EU microbiologists - Biotech companies - The postdoc on the project > How will they benefit? The wider public: Infectious diseases are a serious burden on healthcare. The growing numbers of multi-drug resistant bacteria require the development of new antibiotics and treatments. If we want to be able to fight infectious diseases in the long run, it is pivotal to understand the essential functions of pathogens, including basic processes like protein localization, which is the focus of this proposal. UK scientific competitiveness: Fundamental bacterial cell biological research is a competitive field, and this will attract good scientists from abroad, which will strengthen the scientific competitiveness of the UK. Furthermore, to understand the basic principles that underlie binding of proteins to curved membranes, collaboration with biophysicists is important. If the proposal is successful I will be able to continue my collaboration with Dr. Davide Marenduzzo (Edinburgh University, support letter included). A successful collaboration between experimental biologists and theoretical biophysicists will further add to the scientific competitiveness of the UK. EU microbiologists: Bacterial cell biology is a relative young field and most microbiologists are just starting to incorporate this aspect into their own research. However, often the experience and/or the sensitive high-resolution fluorescence light microscopes necessary for this type of research are not readily available. We provide support for those scientists by setting up collaborations. It is foreseen that the research on protein localization will be of interest to many microbiologist, which will also increase changes to participate in future European research collaborations. Biotech companies: The specific localization pattern of DivIVA in the cell is robust, which makes DivIVA a potential useful biobrick for synthetic biological purposes. However, to fully exploit the possibilities to use DivIVA as a protein targeting tool, it will be necessary to understand how this protein binds to curved membranes and how it recruits other proteins. In addition, Bacillus subtilis is a well known commercial production organism used in the biotech industry to produce enzymes and secondary metabolites. The more we know about the physiology of B. subtilis, the more we can develop and optimize practical applications for this organism. The postdoc on the project: The postdoc has to present the data at international scientific meetings. The presentation skills obtained during the project will be useful in all relevant employment sectors. Moreover, B. subtilis is a model system for Gram-positive bacteria and used in the industry. The wide use of this bacterium will increase employability. > What will be done to ensure that they benefit? The wider public: The results of the research will be published in peer reviewed scientific journals that make their publications readily available to the public (open access policy). UK scientific competitiveness: The RA position will be advertised in international scientific top journals such as Nature and Science, to attract the best scientists. Collaborations with biophysicists such as Dr. Marenduzzo are foreseen. EU microbiologists: The results of the research will be presented at international meetings, and when possible collaborations within EU research frameworks will be initiated. Biotech companies: When it is foreseen that the results of the research has potential commercial relevance, contact with biotech companies will be established. The postdoc on this project: The postdoc will attend international scientific meetings to present the work, and will be trained in relevant genetic and biochemical techniques.

Committee	Research Committee D (Molecules, cells and industrial biotechnology)
Research Topics	Microbiology, Structural Biology
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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