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View History Bookmarks People Window Help ral Physics i: sx Temple University - CHEM 44(xFiles ps://templeu.instructure.com/courses/35332/files?preview-1308991 s.. TUportal-211 N Netflix 2014-2015 Calend . Check Test Place A.. ...ou mi :sssss 0 Philadelphia to Ne.. 018 Practice Exam Il RJS.pdf Download Page of 8ZOOM 6 Initials 8. In the following sequencing steps summarize what is known about the order of the sequence after each step. Note: Use 0 to indicate a peptide composed of the amino acids within the parentheses but whose order is not yet known. In the following sequencing steps summarize what is known about the order of the sequence after each step (20 pts): To start with) Acid hydrolysis of a nonapeptide gave the amino acid composition (Lysa, Arg. Ala, Gly, Ser, Thr, Met, Phe) a) Carboxypeptidase A treatment released Gly b) Trypsin cleavage with the following reagents gave peptide fragments with the indicated composition (Trypsin cleaves at the C-side" of basic residues.): (Ala,Arg) and (Ser,Lys,Phe) and (Lys) and (Gly,Met, Thr) c) CNBr: (Lysa,Arg,Met,Phe,Ala,Ser) and (Gly,Thr) d) Pepsin cleaves at the "C-side" of aromatic residues. You should be able to write out the sequence after considering this observation (no structure necessary) Arg,Ser,Ala) and (Lyse,Phe,Met,Gly.Thr). 18 G Search or type URL

Explanation / Answer

a) Carboxypeptidase cleaves at C-terminus of peptide. It is exopeptidase. It is clear that Glycine is present on C terminus.

b) Trypsin cleaves on Carboxyl side of Arg and Lys. As 4 fragments are given it is clear that 3 cleavage sites are present.

1)Ala, Arg 2) ser phe lys 3)lys 4) met thr gly. Here as we know Gly

is on C terminus , and Lys present 2 times, in the (ser, lys, phe) in this peptide as lys has to be come after ser and phe in order to be get cleaved by trypsin -so we can rearrange sequence asfollows

Ala arg (ser phe) lys lys (met thr) gly

C) CNBr cleaves on carboxyl side of methionine. After cleavage on carboxyl side of met it will give 2 fragments one containing gly thr. but as we know gly is on C terminus we can rearrange sequence as thr gly.

so we can rearrange sequence as follows.

Ala arg( ser phe )lys lys met thr gly.

d) pepsin cleaves on amino side of phe, tyr and trp. As phe is present in given sequence it will give 2 peptides. one will have ala arg ser sequence. so it is clear that phe comes after ser. so it can be rearranged as follows.

Ala Arg Ser Phe Lys Lys Met Thr Gly. This sequence is present in the peptide.

Note:- In the provided data it is written that pepsin cleaves Carboxyl side of aromatic amino acids. Actually pepsin cleaves amino side of aromatic amino acid.

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