Post-graduate theses
Current Record: 4906 of 6549
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| Identifier |
uch.biology.msc//2007mpariami |
| Title |
Χαρτογράφηση των θέσεων αλληλεπίδρασης ανάμεσα στη SecA και το κανάλι του SecYEG |
| Creator |
Mpariami, Vassiliki
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| Abstract |
The Sec machinery is a universally conserved multi-component enzyme complex involved in two biological key processes: integration of membrane proteins into lipid bilayers and translocation of preproteins across these bilayers. In bacteria a central role in both processes is fullfilled by the integral membrane complex SecYEG that forms the protein conducting channel within the cytoplasmic membrane. Two different cytoplasmic partners can bind to SecYEG to induce opening of the channel . Membrane proteins are mostly inserted co-translationally by SecYEG bound ribosomes whereas secretory proteins and large extracellular domains of integral membrane proteins are translocated post-translationally by the motor protein SecA. The last five years have been characterized by a tremendous progress in our structural view on protein translocation, by the appearance of high resolution crystal structures of individual components and medium resolution cryo-electron microscopy structures of co-translational translocation intermediates. Despite these structures there remains a large gap in our understanding of the interactions between the individual components and most notably on the highly dynamic interaction between SecYEG and SecA. The motor protein SecA binds to the SecYEG translocation channel. Once bound SecA undergoes conformational changes that result in translocation of the pre-proteins. During the initiation phase of translocation the conformational changes of SecA are transmited to SecYEG resulting in opening of the channel and co-insertion of the signal sequence whereas in latter stages SecA has been shown to insert into the SecYEG complex. Despite the fact that the interaction has been studied extensively, relatively little is known about the regions of SecYEG that mediate it. Peptide scanning technology has been used to identify regions in SecYEG that interact with SecA. Binding experiments held at 4οC indicated cytoplasmic regions C1, C2, C4, C5, C6 as well as the periplasmic region P3 and the transmembrane region TM9 of SecY as putative interaction sites. At the same time SecA binding peptides at 37οC are mapping in more internal regions of the protein, that correspond to transmembrane regions TM1, TM2b,TM3, TM6, TM7, TM8, TM9, TM10 and periplasmic region P5. Highly conserved residues amongst those regions were selected and subjected to extensive mutagenesis. In vivo complementation experiments left us with a number of SecY mutants that had a severe growth defect. Control experiments have shown that these defects could not be attributed to either lack of expression nor to improper localization of the membrane embedded SecYEG complex. We suggest that those regions are putative interaction sites between SecA and SecYEG.
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| Issue date |
2007-09-01 |
| Date available |
2007-07-09 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/e/c/8/metadata-dlib-2007mpariami.tkl
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| Views |
248 |
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