Amyloid β (Aβ) polypeptide plays a key role in determining the state of protein aggregation in Alzheimer’s
disease. The hydrophobic C-terminal part of the Aβ peptide is critical in triggering the transformation from α-helical to β-
sheet structure. We hypothesized that phospholipase A2 (PLA2) may inhibit the aggregation of Aβ peptide by interacting
with the peptide and keeping the two peptide chains apart. In order to examine the nature of interactions between PLA2
and Aβ peptide, we prepared and crystallized complex of Naja naja sagittifera PLA2 with the C-terminal hepta-peptide
Val-Gly-Gly-Val-Val-Ile-Ala. The X-ray intensity data were collected to 2.04 A resolution and the structure was
determined by molecular replacement and refined to the crystallographic R factor of 0.186. The structural analysis
revealed that the peptide binds to PLA2 at the hydrophobic substrate binding cavity forming at least eight hydrogen bonds
and approximately a two dozen Van der Waals interactions. The number and nature of interactions indicate that the
affinity between PLA2 and the hepta-peptide is greater than the affinity between two Aβ peptide chains. Therefore, PLA2
is proposed as a probable ligand to prevent the aggregation of Aβ peptides.
Keywords: Alzheimer's disease, Aβ peptide, C-terminus, co-crystallization, phospholipase A2, VGGVVIA.
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