MEMBRANE PROTEASES · Structural determination and mechanistic understanding of membrane proteases
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2007-04-01 → 2009-04-01
- EU contribution
- €159,046
- Participants
- 1
- Scheme
- EIF
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Results in brief
Final Activity Report Summary - MEMBRANE PROTEASES (Structural Determination and Mechanistic understanding of Membrane proteases.)
Cellular signalling is an important biological process in eukaryotic cells through which they communicate. Regulation of such signalling is critical since unchecked signalling can lead to cancer. Recent identification of intra-membrane proteases has revealed a new strategy for cellular regulation where transmembrane proteins, which are inactive in their membrane bound form, are activated by intra-membrane proteolytic cleavage. Proteolysis results in the release of cytoplasmic, luminal or extracellular domains that move to new locations where they can carry out their biological function. Different intra-membrane protease families, classified as serine, aspartyl or metalloprotease have been identified in all life kingdoms. The primary objective of the project was the determination of intra-membrane proteases structures, along with their mechanistic understanding. My focus was on two of these families, namely rhomboid, an intra-membrane serine protease, and gamma secretase, an intra-membrane aspartyl protease. Rhomboids are widely distributed in all organisms and are involved in diverse processes, such as quorum sensing in bacteria, differentiation and growth factor signalling in eukaryotes. I was successful in obtaining two-dimensional and three-dimensional crystals of a prokaryotic homologue of rhomboid protease from escehrichia coli GlpG. The three-dimensional crystals of GlpG provided us with a structure that would enable us to carry out structure-function studies and understand the mechanism of proteolysis. Gamma secretase was a multi-subunit membrane protein complex, involved in cell signalling and generation of Aß (beta) peptide in Alzheimer disease. The major focus was to obtain good amounts of homogenous protein, suitable for cryo-electron microscopy, which would lay a platform for future structural work. Any structural information on intra-membrane proteases would be invaluable for rational design of drugs.
Data: CORDIS, © European Union
Project objective
Proteases are large group of proteins that cleave the amide bond in peptides and proteins. Common properties of all these proteases is the activation of water molecules for catalysis and that the proteins undergo conformational changes upon substrate binding.Hence it came as a surprise when membrane embedded proteases was identified. Proteases residing in the membrane should be able to create a microenvironment for water and the hydrophilic residues required for catalysis and should be capable of bending o r unwinding hydrophobic substrates making them suitable for cleavage.Membrane proteases have been implicated in different processes such as cellular differentiation, in unfolded protein response, lipid metabolism, signal peptide processing and, in prokaryotes, generation of peptide pheromones and response to extracellular stress.These have been collectively termed as Regulated Intramembrane Proteolysis (RIP), which has emerged as a novel mechanism in cell signalling. Some transmembrane proteins are kept inactive in their membrane-tethered form and require proteolysis for activation. Intramembrane proteolysis results in the release of these domains that move to a new location where they can carry out their biological function.Two of the well-studied membrane proteases include the rhomboid proteases involved in the Drosophila EGF receptor pathway and the g-secretase implicated in the processing of amyloid precursor protein (APP) implicated in Alzheimers disease. The membrane proteins belonging to this family have similar catalytic residues as some of the classical soluble proteases.This raises the question how these conserved amino acids embedded in the lipid bilayer have access to and activate water that is required for catalysis, and how the substrate is recruited. To understand this we would like to obtain high-resolution structures of a membrane protease and study the mechanism of intra-membrane proteolysis.
Original text from CORDIS.
Participants
- MEDICAL RESEARCH COUNCIL · LONDONCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union