Question

On your internship, you visit the Mass Spectrometry Lab. Mass spectrometry can identify short peptide fragments based on their molecular weights. Your fellow intern Jerry has neglected to label his tubes of amyloid beta peptide 42 after digesting them with some proteases that we learned about in Module 6: pepsin, trypsin, and chymotrypsin. Help him figure out what protease is in each tube. Jerry’s supervisor has the fragments listed in the same order as the original peptide primary sequence, which is shown as the three-letter amino acid code, left-to-right from the free amino end (N-terminal) to the carboxyl end (C-terminal). Each fragment is listed as a separate line, in order.

Consider the sequence for the amyloid beta peptide 42, which is involved in Alzheimer’s disease:

Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-Val-Gly-Gly-Val-Val-Ile-Ala

Tube A:

Asp-Ala-Glu-Phe

Arg-His-Asp-Ser-Gly-Tyr

Glu-Val-His-His-Gln-Lys-Leu

Val-Phe

Phe

Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu

Met

Val-Gly-Gly-Val-Val-Ile-Ala

Tube B:

Asp-Ala-Glu

Phe-Arg-His-Asp-Ser-Gly

Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val

Phe

Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-Val-Gly-Gly-Val-Val-Ile-Ala

Tube C:

Asp-Ala-Glu-Phe-Arg

His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys

Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys

Gly-Ala-Ile-Ile-Gly-Leu-Met-Val-Gly-Gly-Val-Val-Ile-Ala

Answer 1

Trypsin - cleaves from C terminal Lysine - Lys Arginine - Ang Pepsin - cleaves from ( terminal Phenylalanine Phe Teyp to phan tap Tyrosine - Tyn Chymo taypsin a cleaves from N-terminal Levine – heu Tryptophan - Tap Tyrosine - Tyr Phenylalanine - Phe

Tube A (Chymotrypsin) N-Asp-Ala-Glu- Phe Aeg- His-Arp- Ses-Cly-Tyn, Glu-Val-His-His-Gln-Lys-Lev, Val-Phe Phe! e Ala-Glu-Asp - Val-Gly,- Ses- Arn- Lys-Ely-Ala-lle-lle-Gly-leu Met Val-Gly-Gly-Val-Val- lle - Ala-c Digestion crewed cut phe, Tys, revi Tube B Pepsin C cleavage N-Asp- Ala-Glu Phe-Arg-His-Asp-See-aly The-Chu Val-His-flis-Gln-Lys- Zeu-val Phe Phé-Ala-alu-Asp - Val-aly-

Ser - Asn-lys-aly - Ala-lle-lle- Gly- Lev- Met -Val-Cly-lily- Val- valolle - Ala - (', As digestion occined at Tye, Pheonly. Tube c leypsin N-Asp- Ala-alu- Phe-Hig His-Asp-Sex-Gly-Tys-celu- val-His- His - Cali - Lys Lev- Val- Phe - Phe - Ala-alu- Asp - Val-aly - Ses - Asn-Lys, Aly-Ala-lle-lle-Aly-Leu-met val-Cly-Cly- Val- Val-lle-Ala Lysinly digestion occued at Lysine & Arginine from c ternu nat