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Flashcards in BC 19 PTM Deck (15):
1

PTM required assembly

1 Folding
2 covalent modification
3 binding

some of these need PTM to occur, not mutually exclusive

2

Folding

Chaperones
-proteins usually fold so hydrophobic cores are at center, awary from water
-presence of hydrophobic molecules on outside lets chaperone know it is unfolded
-bind to small stretches of hydrophobinc AA to initiate or correct protein folding

assisted by HEat Shock Protiens HSP
-chaperones are catalyst, that assemble without being part of assembly
HSP 70
-recruited, bind to stabilize unfolded/misfolded form, DURING translation
-uses ATP for correct folding, required
-cannot fold, give to proteasome machinery for burn

3

Signal Sequences

delivery to a specific organelle

n terminus or c terminus

or protein folding can bring AA together that create a signal patch

advantave of sequence vs patch it can be removed easily at destination

ER signal sequence-first use of a signal sequence occurs while protein is still being translated
-cotranslational instertion
-recruitment of ribosomes to ER surface is by Signal recognition particle (SRP): recognizes and binds SS
SRP receptor: within ER membrane binds SRP
GTP HYDROLYSIS REQUIRED

LOOK AT IMAGE

4

Phosphorylation

most wide spread and reversible PTM

addition of phosphate group to serine threonine or tyrosine

presence or abses of single phosphate froup on key reg protein determins cancer or no

T286 mutation in cyclin D1, phosphorylation normally exports to nucleus, and subsequent to cytoplasm, loss of phosphorylation causes accumulation in nucleus, in esophageal cencer and increases onco potention

5

Acetylation

HATS: loosen chromatin
-acylated makes it looser, hyperacylated competent for transcription and recombination


HDAC: tighten chromatin

6

methylation

transfer of one carbon methyl group to a substrate,
-methyltransferases

SAMe (s-adenosylmethionine) primary methy group donor
-occurs so much SAM super useful substrate
-gene regulation, histone methylation regulates DNA availability
-mono-di-tri methylation

7

Disulfide Bonds

protein Disulfide isomerase (PDI)

assist to form DiS between two cysteine residues (assists doing them correctly)

located only in ER, can only occur in ER

8

N linked Glycosylation

Most common glycosylation

addition of sugars (N linked- Aspargine (N)) NOT N TERMINUS

-can be large branched glycan, begins in cytosol with two n acetyl glucosamine sugars, modifying reside in ER and golgi

9

O linked glycosylation

takes place in lumen of Golgi

covalent addition of n-acetyl galactosamine to OH croup of either serine or threonine

only ONE SUGAR AT A TIME no branched chains

on mucin protiens, and PG of ECM

10

Carboxylation

PTM of glutamate to gamme carboxyglutamate
-blood clotting cascade
-each unaltered glutamate has one negatively charged carbonyl group COO-, but after carboxylation reaction, it has two
-calcium binds to carboxyglutamate and bring these factors to the negatively charged platelet surface

11

Ubiquitination

Rapid proteolysis by Ubiquitin (Ub)

76 AA polypeptide

covalently attached to lysine residues of the tarted protein by ubiquitin ligase

Ub molecule can also be covalently attached to eachother forming chains ultimately binding to single lysine residue

Ubiquitination use to degrade misfolded protiens and can be used for degredation

polu Ub sent to proteasome

12

Ub pathway

E1, E2, E3
-Activation of Ub by being attached to E1
-E1(Ub activating enzyme) binds to Ub donates activated Ub to E2
-E2 (Ub conjugating enzyme) catalyzes covalent addition of Ub to Protien substrates
-E3 (Ub accessory protein) confers specificity, to Ub allows binding of substrates but does not actually catalyze transfer of Ub
-E2E3 complex togher called ubiquitin ligase

13

Proteasome

Ub proteins degraded by ATP dependent multiprotien subunit called proteasome

barrel shaped complex binds, unfold and threds linear PP into protein core at center

digested into peptides

Ind ubiquitin molecules are released intact and reused

14

Hypoxia

low O2 pathological condition

O2 sensed by kidney

kidney secretes EPO which stim the prod of RBCs in BM

controlled by PTM of hypoxia induced factor 1 HIF1

15

HIF1alpha

O2 sensing is possible by O2 dependant ubiquitination of TF HIF1alpha.

HIF1alpha is a substrate for cytoplasmic enzyme prolyl hydroxylase

Proline hydroxylation of HIF1alpha requires O2. Once the proline residues are dydoxylated the protein con be recognized by E3 component of Ub Ligase that targets it for degredation by lysosome.

Under low O2 PH cannot function and hydroxyproline residues not created. E3 connot bind

HIF1alpha translocated to nucleas where with HIF1beta it can increase the expression of a number of hypoxia related genes including EPO

the kid is then able to synth EPO to return O2 levels and HIF1alpha degraded again