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Quantification of Protein-Lipid Interaction Exemplified for SecA Protein / submitted by Anika Schorpp
AuthorSchorpp, Anika
CensorGruber, Hermann
PublishedLinz, 2017
Description70 Blätter : Illustrationen
Institutional NoteUniversität Linz, Masterarbeit, 2017
Document typeMaster Thesis
Keywords (GND)Plasmamembran / Proteine / Lipide / Translokation
URNurn:nbn:at:at-ubl:1-21174 Persistent Identifier (URN)
 The work is publicly available
Quantification of Protein-Lipid Interaction Exemplified for SecA Protein [2.33 mb]
Abstract (English)

The SecA protein, together with the SecYEG protein complex, is crucial for the translocation of post-translationally translocated outer membrane proteins. SecA thereby acts as the motor protein which pushes the polypeptide chain through the SecYEG translocon. It has been demonstrated, that functional high-affinity binding of SecA to the membrane not only requires the SecYEG complex, but also the presence of acidic phospholipids. The aim of this master thesis was to further characterize the interaction between the SecA protein and negatively charged phospholipids. Therefore, the two complementary BIA techniques, surface plasmon resonance (SPR) to measure the interaction at the sensor surface and microscale thermophoresis (MST) for analysis in homogeneous solution, were used. Initially we tried to measure the interaction between SecA and different lipid vesicles which were immobilized on the recently developed desthiobiotin sensor chip via biotin-residues. However, due to the unknown effect of the biotin-residues on the SecA binding, we decided to instead use the traditional lipid chips, the HPA and the L1 sensor chip. The unusual curve form of the results from these sensor chips made it impossible to quantitatively analyze the measured binding curves, which is why the measurements were evaluated by determining the extent of SecA binding. On both lipid sensor chips, a high amount of SecA binding to immobilized lipid vesicles containing a net negative charge (PLE and PEPG vesicles) was observed in contrast to very low SecA binding extents to lipid vesicles that possess a neutral net charge (PC vesicles). These results were confirmed by the MST measurements, whereby it was only possible to determine an equilibrium dissociation constant for the measurements between SecA and lipid vesicles that possess a net negative charge.

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