41. A protein is subjected to cyanogen bromide treatment,...

41. A protein is subjected to cyanogen bromide treatment, which hydrolyzes peptide bonds after methionine side chains. One of these cyanogen bromide fragments is purified and split into two tubes. Trypsin is added to one tube, while chymotrypsin is added to the other tube. The tryptic and chymotryptic fragments were then sequenced. The sequencing results for each fragment are listed below. Tryptic Fragments Chymotryptic Fragments T1: Y-T-K T2: W-I-L-E T3: A-D-R C1: I-L-E C2: A-D-R-Y C3: T-K-W What is the sequence of the original fragment that was produced by the cyanogen bromide treatment? A. ADRYTKWILE B. YTKWILEADR C. ADRWILEYTK D. YTKADRWILE E. ILEYADRWYTK

Transcript

00:02 So now i did a little bit of pre -work on this one just because i thought it would be a bit long if i wrote out every single section.

00:11 So tripsin cleaves on the c terminal of argonyonyl lysine.

00:16 So as you can see here, that means that they have to be at the end of the sequence with a new thing starting the sequence.

00:23 So we know that argonine and lysine need to be exactly one, two, three away from each other.

00:30 Now these aren't in order, but this is just where they're cleaved.

00:33 So chymo -tripsin or tripsin, camo -tripsin, cleaves the aromatic amino acids of the c terminal.

00:43 So that means they need to be at the end of the sequence.

00:46 So in this sequence, we know that this one needs to be at the end, this one is to be at the end, and then this one needs to be at the end, and this one needs to be at the end.

00:58 And then cyanogen bromide showed that methyanine was cleaved at the c terminal.

01:02 So from there, we know that methyanine goes at the beginning of our sequence because everything else comes after it.

01:13 Now we can build our peptide.

01:16 Let's look at everything else that was with methyanine.

01:19 Okay, so this is our next segment.

01:22 So we know from the way that it was cleave, methyonine was in the middle here.

01:29 So the next thing that's probably attached to it, we know that the lysine needs to be included as the beginning of this sequence and needs to be next to a trypsin.

01:51 That's all we really know and we know that the tyrosine needs to be next to the glycine.

01:58 But we don't really have a preference of where the valley goes.

02:03 So we know that the lysine can't be next to the valline, and to not the valine.

02:08 It can't be close to the tyrosine, but that's about it...

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