Figure 4. Phenylalanine mutations in the P2’ position of the last read tripeptide segment dictates final pathway preference.
(A) Aβ42/40 ratios from HEK cells of V44F-M51F and I47F-M51F double mutants behave like single Phe mutants V44F and I47F, respectively. Aβ levels measured by 4G8 ELISA. Mean ± SD, n = 3, t-test **<0.01, ***<0.001. (B) Aβ42/40 ratios from HEK cells of I45F-V50F and T48F-V50F double mutants behave like single Phe mutants I45F and T48F, respectively. Aβ levels measured by 4G8 ELISA. Mean ± SD, n = 3, t-test *<0.05, **<0.01, ***<0.001, ****<0.0001. (C) MALDI/TOF MS conformation of the elimination of AICD 49–99 and AICD 50–99 for the V50F and M51F containing double Phe mutants, respectively. V44F-M51F (AICD 49–99, expected mass: 7034.8, observed mass: 7030.7; AICD 47–99 expected mass: 7249.0, observed mass: 7253.7), I45F-V50F (AICD 50–99, expected mass: 6953.8, observed mass: 6950.1; AICD 48–99, expected mass: 7167.9, observed mass: 7164.6), I47F-M51F (AICD 49–99, expected mass: 7034.8, observed mass: 7032.2; AICD 47–99, expected mass: 7283.0, observed mass: 7280.1), T48F-V50F (AICD 50–99, expected mass: 6953.8, observed mass: 6949.4; AICD 48–99, expected mass: 7214.0, observed mass: 7209.4). (D) Aβ42/40 ratios from HEK cells transfected with double Phe mutations in tandem. Aβ levels measured by 6E10 ELISA. Mean ± SD, n = 3, t-test **<0.01, ***<0.001, ****<0.0001.