C-terminal PAL motif of presenilin and presenilin homologues required for normal active site conformation
Article first published online: 23 NOV 2005
Journal of Neurochemistry
Volume 96, Issue 1, pages 218–227, January 2006
How to Cite
Wang, J., Beher, D., Nyborg, A. C., Shearman, M. S., Golde, T. E. and Goate, A. (2006), C-terminal PAL motif of presenilin and presenilin homologues required for normal active site conformation. Journal of Neurochemistry, 96: 218–227. doi: 10.1111/j.1471-4159.2005.03548.x
- Issue published online: 23 NOV 2005
- Article first published online: 23 NOV 2005
- Received September 1, 2005; resubmitted manuscript accepted September 6, 2005.
- Alzheimer's disease;
- intramembrane-cleaving aspartyl proteases;
- signal peptide peptidase
The Alzheimer's disease-associated β-amyloid peptide is produced through cleavage of amyloid precursor protein by β-secretase and γ-secretase. γ-Secretase is a complex containing presenilin (PS) as the catalytic component and three essential cofactors: Nicastrin, anterior pharynx defective (APH-1) and presenilin enhancer-2 (PEN-2). PS and signal peptide peptidase (SPP) define a novel family of aspartyl proteases that cleave substrates within the transmembrane domain presumptively using two membrane-embedded aspartic acid residues for catalysis. Apart from the two aspartate-containing active site motifs, the only other region that is conserved between PS and SPP is a PAL sequence at the C-terminus. Although it has been well documented that this motif is essential for γ-secretase activity, the mechanism underlying such a critical role is not understood. Here we show that mutations in this motif affect the conformation of the active site of γ-secretase resulting in a complete loss of PS binding to a γ-secretase transition state analog inhibitor, Merck C. Analogous mutations in SPP significantly inhibit its enzymatic activity. Furthermore, these mutations also abolish SPP binding to Merck C, indicating that SPP and γ-secretase share a similar active site conformation, which is dependent on the PAL motif. Exploring the amino acid requirements within this motif reveals a very small side chain requirement, which is conserved during evolution. Together, these observations strongly support the hypothesis that the PAL motif contributes to the active site conformation of γ-secretase and of SPP.