PMC

(A) non-protonated acetamide and Tyr- Tyr-OPO3H-. (B) Protonated acetamide and Tyr-OPO3H-, where the involved oxygens on Tyr-OPO3H- are both not protonated. (C) Protonated acetamide and phosphorylated tyrosine, where the protonated C=O on acetamide interacts as a proton donor with the protonated P-O on Tyr-OPO3H-. (D) Protonated acetamide and Tyr-OPO3H-, where the protonated C=O on acetamide interacts as an electron lone pair donor with the protonated P-O on Tyr-OPO3H-.

Normalized ion counts registered during the N-methylmethanimine (MMI) photo-oxidation experiment on 2016.12.14. Signals: m/z 44.052 (C₂H₆N⁺, protonated CH₃N=CH₂), 43.054 (C₃H₇⁺, fragment of IPN), 31.019 (CH₃O⁺, protonated CH₂O), 32.050 (CH₆N⁺, protonated CH₃NH₂), 30.034 (CH₄N⁺, protonated CH₂=NH), 77.035 (CH₅N₂O₂⁺, protonated CH₃NHNO₂), 58.029 (C₂H₄NO⁺, protonated CH₃NCO and/or CH₂=NCHO), 60.045 (C₂H₆NO⁺, protonated CH₃N=CHOH and/or CH₂=NCH₂OH), and 42.034 (C₂H₄N⁺, fragment of protonated CH₃N=CHOH and/or CH₂=NCH₂OH).

(A) MS analysis of hIAPP incubated with recombinant BACE2; the predicted peaks are indicated: 1–37, 24–37, 1–15, 16–37 and 1–23. (B) Co-incubation with recombinant human insulin blocks BACE2-mediated digestion of hIAPP. (C) Co-incubation with recombinant human proinsulin does not prevent BACE2-mediated digestion of hIAPP. (D) hIAPP plus recombinant human insulin: Single protonated IAPP (m/z 3903) and double protonated IAPP (m/z 1952); single protonated insulin (m/z 5806) and double protonated insulin (m/z 2903). (E) hIAPP plus recombinant human proinsulin; single protonated IAPP (m/z 3903), double protonated IAPP (m/z 1952), double protonated proinsulin (m/z 5250), triple protonated proinsulin (m/z 3495), and quadruple protonated proinsulin (m/z 2625). (F) Recombinant insulin is unchanged by recombinant BACE2. (G) Recombinant proinsulin is unchanged by recombinant BACE2. (H) Recombinant insulin alone and (I) recombinant proinsulin alone. All reactions were performed in PBS, pH 7 for 4 hours at 37°C. Peptide fragment sequences detailed in .

Ligand interaction map of the predicted binding mode of A) 32R-isomer protonated, B) 31R-isomer protonated, C) 31S-isomer deprotonated, D) 32S-isomer protonated, E) 33R-isomer protonated, F) BI-D1870 S-isomer protonated, G) BI-D1870 R-isomer protonated, H) 44 protonated/deprotonated, I) 28R-isomer protonated, and J) 28S-isomer protonated in the ATP-binding site of the RSK2 NTKD, where red residues are charged negative, purple residues are charged positive, green residues are hydrophobic, and blue residues are polar, magenta arrows indicate H-bonds, violet lines indicate slat bridges, and gray spheres represent areas of solvent exposure.