Lecture 11

Question 1

What is an srp

Give an example

Answer 1

A signal recognition particle

A ribonucleoprotein

Question 2

What is a signal peptide

Answer 2

The n terminal sequence of a pre protein that gets cleaved off

Also called a leader sequence

Question 3

How do signal recognition particles (SRP) and signal sequences interact

Answer 3

The ribosome is making the protein and adds a n terminal signal sequence to it

The sequence is recognized by the SRP

SRP takes the ribosome to the ER membrane

Protein gets made and released into the ER where the signal peptide is removed and the protien can fold

Question 4

What does the processing of insulin require

Answer 4

PTM

Question 5

What is the steps of processing insulin

Answer 5

A: preproinsulin: insulin with signal sequence

B: proinsulin: the signal sequence is cut off but this is still not active form of the final product

C: insulin: the terminus is cut off , now active dimer

Question 6

What’s an example of a proprotein

What’s the active form of this

What would it have if it were a preoproprotein

Answer 6

Zymogen

Requires a type of cleavage to become active

Trypsin

Would have a signal sequence

Question 7

When does the first cut of a preproprotein (cleave singal sequence ) happen

The. The second cut

Answer 7

First cut happens right as it gets translated and goes into the er, so its now proprotein

2nd cut happens in the secretory vesicles of the golgi now protein

Now active

Question 8

What is glycosylation

What does it help with

Answer 8

Attaching carbohydrates to proteins

Solubility and stability

Shield against degredation (since glycosylation is a big structure)

Act as a label for recruitment or target proteins to specific areas of the cell

Question 9

What are the types of extracellular glycosylation

Answer 9

N linked: on asparagine primary amine

O linked: on ser or thr oh

O linked less common

Question 10

What are the types of intracellular glycosylation

Answer 10

Only a single sugar gets attached
Which is N acyetlglucosamine (glcNAc)

Question 11

What is the motif for n linked glycosylation

Answer 11

Asn -x- ser/thr

Ser or thr

X is Any except proline

Question 12

Glycosislation starts and ends where

Answer 12

Starts in the er then to the golgi then protein with sugar gets secreted

Question 13

What is GlcNAC

Answer 13

N-acetylglucosamine

This gets added to the asparagine for n linked glycosylation

Question 14

What is DPP (dolichol pyrophosphate)

Answer 14

Spans the ER membrane and more and more sugars get added to it by UDP (uridine diphosphate, carrier of sugars)

The DPP with 5-6 sugars eventually flips to the other side of the membrane (through the use of flippase)

Then the sugars (now in the ER lumen) get added on to the target protein

Question 15

ALL N LINKED ARE MADE IN

Answer 15

The ER

Then secreted to the golgi

Question 16

All glycosyltranferase need a

Answer 16

UDP to attach sugars to DPP

Question 17

If glycosylation happens intracellular how does it happen

Answer 17

Only one sugar is added and the protien is not flipped (since already in the intracellular cell)

Mainly a eukaryotic thing

Question 18

What’s sugar is added in n linked

And o link

Answer 18

GlcNAC

Galnac

Question 19

What makes region of the histone more of less accessible

What does this mean

Answer 19

PTM

PTM can regulate transcription

Question 20

What PTM happen on histone tails

Answer 20

Acetylation

Methylation

Phosphorylation

Question 21

How many types of histone are wrapped around the DNA

Answer 21

4

H2A H2B H3 H4

Question 22

The tails of histones do what

Answer 22

They recruit proteins and molecular markers to either turn the genes on or off

Question 23

The backbone of dna is _____ charged

What does this mean for histones

Answer 23

negatively due to phosphate

This means dna is bound tightly to the + histones

Question 24

When dna less tightly bound what metal causes this to happen

Answer 24

Mg2+ since it bound to atp most of the time

Counteract the charge of histone proteins

DNA might be more exposed due to being bound to mg rather than the histone protein

Question 25

What is lysine acetylation

Answer 25

Acetyltranferase (HAT) puts acetyl on lysine in the tail

The acetyl cancels the + charge of the histone tail

Now histone not tight bound to dna

Backbone exposed and transcription happens

Question 26

What is lysine methylation

What is used as a methyl donor

Answer 26

Done by its own methyltransferase

Can and 1 2 or 3 methyl’s to the amine of lysine

Makes the lysine more hydrophobic, so it cancels the charge interaction with the dna

since sticky it can recruit also another protein

They use SAM as a methyl donor

Question 27

What is argenine methylation

Answer 27

Can methylate on either side of the nh2 of the arg guanidinium group

Assymetric: bith methyl’s on one nh2

Symmetric: one methyl on each nh2

Usually no trimethylation because of steric hindrance

Question 28

What is the histone code

Answer 28

Many PTM arrangement on histone tails a required together to have an effect

These many modifications is the histone code

Question 29

What are bromodomains

Answer 29

Domain on another protein that recognizes histone acetyl groups on lysine

Not a protein itself, it’s a domain

Question 30

What are chromodomains

Answer 30

Recognize methylated lysines or Argentines on histones

Ex. If something has a HAT domain, and a bromodomain actelyate. It’s target first need to be acetylated so the bromo domain recognizes it then it can do HAT

Question 31

Proteins can have both

Answer 31

Bromo and chromodomains