The Major Allergen from Birch Tree Pollen, Bet v 1, Binds and Permeabilizes Membranes
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- 作者：Jesper E. Mogensen ; Mercedes Ferreras ; Reinhard Wimmer ; Steen V. Petersen ; Jan J. Enghild ; Daniel E. Otzen
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：March 20, 2007
- 年：2007
- 卷：46
- 期：11
- 页码：3356 - 3365
- 全文大小：229K
- 年卷期：v.46,no.11(March 20, 2007)
- ISSN：1520-4995
文摘
The 159 residue Bet v 1 is the major allergen from birch tree pollen. Its natural function isunknown although it is capable of binding several types of physiologically relevant ligands in a centrallyplaced cavity in the protein structure. Here we use circular dichroism and fluorescence spectroscopy toshow that Bet v 1 binds to DOPC and DOPG phospholipid vesicles in a pH-dependent manner. Bindingis facilitated by low pH, negatively charged phospholipids, and high vesicle curvature, indicating thatelectrostatic interactions and vesicle surface defects are important parameters for binding. Binding isaccompanied by major structural rearrangements, involving an increase in 
-helical structure and a decreasein 
-structure. A bilayer structure per se is not a prerequisite for these rearrangements, since they alsooccur in the presence of the micelle-forming lysophospholipids lysoMPC and lysoMPG. Two major boundstates (A and B) with distinct secondary structure compositions were identified, which predominate in thepH ranges ~9.5-6.5 and ~5-2.5, respectively. Despite the high content of secondary structure, the A-and B-states are partially unfolded as they unfold noncooperatively in CD thermal scans, in contrast tothe native state. In addition, the B-state (but not the A-state) shows intermediate proteolysis-resistanceand is able to induce complete leakage of calcein from the vesicles, indicating that this state is partiallyinserted into and significantly perturbs the bilayer structure. We conclude that Bet v 1 is a membranebinding protein, highlighting a possible biological function of this protein.
-helical structure and a decreasein -structure. A bilayer structure per se is not a prerequisite for these rearrangements, since they alsooccur in the presence of the micelle-forming lysophospholipids lysoMPC and lysoMPG. Two major boundstates (A and B) with distinct secondary structure compositions were identified, which predominate in thepH ranges ~9.5-6.5 and ~5-2.5, respectively. Despite the high content of secondary structure, the A-and B-states are partially unfolded as they unfold noncooperatively in CD thermal scans, in contrast tothe native state. In addition, the B-state (but not the A-state) shows intermediate proteolysis-resistanceand is able to induce complete leakage of calcein from the vesicles, indicating that this state is partiallyinserted into and significantly perturbs the bilayer structure. We conclude that Bet v 1 is a membranebinding protein, highlighting a possible biological function of this protein.