Post translational modifications part 1

virtually all proteins undergo some form of post-translational modification to facilitate:

1. correct …

2. … function

3. other aspect of …

1. folding

2. enzymatic

3. function

post-translational modifications for basic protein function

1. protein …

2. protein … to correct …

3. … interactions

4. … activity

1. folding

2. trafficking, organelles

3. protein protein

4. enzymatic

post-translational modifications to regulate protein function

1. … activity

2. … formation

3. … structure - … code

4. protein …

5. protein …

1. enzymatic

2. complex

3. chromatin, histone

4. localization

5. stability

4 main types of PTMs

1. … changes

2. changing the … nature of … …

3. addition of … …

4. addition of other … or …

1. structural

2. chemical, amino acids

3. functional groups

4. proteins or peptides

2 examples of PTMs involving structural changes

disulphide bridges and proteolytic cleavage

2 examples of PTMs involving chemical changes to amino acids

citrullination and deamination

in citrullination … is converted into …

arginine, citrulline

in deamination … and … are converted to … and … respectively

asparagine and glutamine, aspartate and glutamate

7 examples of PTMs involving addition of functional groups

1. phosphorylation

2. methylation

3. acetylation

4. glycosylation

5. s nitrosylation

6. hydrophobic groups

7. cofactors

S-nitrosyaltion is the attachment of a … … group (…) to a … (…) on the cysteine amino acid, creating an … (…)

nitric oxide, NO, thiol, SH, S nitrothiol, SNO

2 examples of PTMs involving addition of other proteins or peptides

ubiquitination and sumoylation

in sumoylation a … protein is … added to a .. residue on a target protein

SUMO, covalently, lysine

what does SUMO protein stand for?

small ubiquitin-like modifier

2 examples of non-covalent modifications

addition of metal ions and cofactors

metal ions play … as well as … roles in proteins

regulatory, structural

5 examples of metals used to non-covalently modify proteins

iron, zinc, magnesium, copper and nickel

examples of enyzmes containing the following

1. magnesium

2. copper and nickel

3. iron

4. zinc

1. ATP enzymes

2. SOD and antioxidants

3. hemoglobin and cytochromes

4. zinc finger domains and carbonic anhydrase

name the three important parts of a kinase

1. N lobe

2. C lobe

3. A loop

the N-lobe is the … half of the catalytic domain of a kinase and primarily binds and coordinates …

the C-lobe is the … half of the catalytic domain of a kinase and binds the … … and drives catalysis

the A loop, also called the … loop is a … chain that acts as an on/off …

N terminal, ATP

C terminal, protein substrate

activation, peptide, switch

many kinases contain Mg to overcome the … barrier due to the … charge of ATP

electrostatic, negative

which parts of preproinsulin are removed to form the active insulin hormone?

connecting and leader sequences

preproinsulin → … → insulin

proinsulin

proinsulin has lost the … sequence but still contains the … sequence

leader, connecting

a … … (leader sequence) is a short peptide present at the … terminus of the majority of newly synthesised proteins destined towards the … pathway

signal peptide, N, secretory

how many disulphide bridges do immunoglobulins contain?

16

… … … (MBP) is a … protein that helps form and maintain the protective … sheath around …

myelin basic protein, structural, myelin, nerves

… is a critical … protein that binds … fibers together in the outer layer of the skin

filaggrin, structural, keratin

3 examples of protein containing citrulline residues

1. myelin basic protein

2. filaggrin

3. histones

citrullination controls … … particularly in the developing embryo

gene expression

the immune system often attacks … proteins leading to autoimmune diseases such as … … and … …

citrullinated, rheumatoid arthritis and multiple sclerosis

myristoyl anchor → … linkage between terminal amino group and … acid

palmitoyl anchorage → … linkage between … of cysteine and … acid

amide, myristic

thioester, thiol, palmitic

2 examples of anchorage which can connect protein to the plasma membrane through the addition of hydrophobic groups

myristoyl and palmitoyl

does acetlyation of histones activate or repress transcription?

activate

does methylation of histones activate or repress transcription?

both

methylation and acetylation target and modify amino acid residues on which part of histones?

histone tails

acetylation and methylation of histones alter the extent to which DNA is … around histones and the availability of … to be transcribed

wrapped, genes

practically every membrane protein undergoes which modification?

glycosylation

which PTM is the most common and abundant?

glycosylation

glycosylation is the post-translation attachment of … or … … to proteins

sugars or sugar chains

glycosylation is important for …, … and … (3 S) of proteins and … interactions

structure, stability and solubility, cell cell

glycosylation modifications are used by immune system to detect … and …

they are also used by … and … to evade immue system (… for example)

DAMPs and PAMPs

viruses and parasites, HIV

6 examples of glycosylation modifications (FSMGGG)

1. fructose

2. sialic acid

3. mannose

4. galactone

5. GalNAc

6. GlcNAc

what do GlcNAc and GalNAc stand for?

N acetylglucosamine and N acetylgalactosamine

two main types of glycans?

N and O glycans

for N-glycans the attachment site is the … atom of …

for O-glycans the attachment site is the … atom of … or …

N, asparagine

O, serine or threonine

N-glycosylation is … and starts in the … and ends in the …

O-glycosylation is … and occurs in the …

cotranslational, ER, golgi

post translational, golgi

what are the two possible sequons of amino acid residues at which N-glycosylation occurs (and also what amino acid cannot be X)

asn x ser and asn x thr, proline

the … chains of immunoglobulin … are N-glycosylated at a conserved site

heavy, G

N-linked glycosylation is an essential … component that is added to the … polypeptide in the … and is involved in intial steps of protein …

structural, nascent, ER, folding

2 main types of N-linked oligosaccharides in glycoproteins

complex and high mannose oligosaccharides

both … and … oligosaccharides share a common … region derived from the original N-linked oligosaccharide added in the ER which typically contains two … and three …

complex and high mannose, core, GlcNAc, mannoses

N-glycosylation is a … driven process meaning the cell does not use a direct … blueprint to dictate the … of the glycan chains attached to proteins

nontemplate, genetic, structure

antibodies contain two … chains each of which consists of … … domains and two … chains each of which consist of … … domains

light, 2 Ig, heavy, 4 Ig

antibodies induce … responses following … and contribute to immune … formation

effector, opsinisation, complex

communication with immune cells is mediated by the … region of antibodies and … is critical for this interaction

Fc, glycosylation

in antibodies the … region is important for … binding and the … region affects … activity

Fab, antigen, Fc, IgG

transmembrane … glycoproteins perform important … functions in … epithelia

their large … and heavy … make these molecules highly effective

mucin, barrier, mucosal

size, glycosylation

MUC1’s barrier functionality is exploited by many … as it is … and distributed over the entire cell surface to create a local … which protects the cells from host … system and promotes … activity

carcinomas, overexpressed, microenvironment, immune, metastatic

… residues act as the critical terminal carbohydrate anchors that … proteins recognise and bind to mediate cell … in the …

sialylated, selectin, adhesion, bloodstream

mucins are a group of … and … rich proteins that are heavily … and their extended structure allows them to present … carbohydrate ligands to …

serine and threonine, glycosylated, sialylated, selectins

Migration of T cells into lymph nodes

the … on leukocytes recognises … carbohydrates on two … like molecules (… and …) expressed on certain … cells of … nodes

L selectin, sialylated, mucin, CD34 and GlyCAM 1, epithelial, lymph

O-linked glycans

are built up in a stepwise fashion with sugars added …

glycosylation occurs when the protein is fully …

glycosylation carried out by … bound enzymes called … … which reside in the … or …

incrementally

folded

membrane, glycosyl transferases, ER or golgi

some … and … proteins have a single … residue …-linked to a … or … residue

cytoplasmic and nuclear, GlcNAc, O, serine or threonine

O-GlcNAcylation plays an important role in the modulation of the activity of … proteins and in some proteins the ser/thr residue may be subject to competing … and …

intracellular, phosphorylation and O glycosylation

enzyme which adds O-linked GlcNAc

enzyme which removes O-linked GlcNAc

O GlcNAc transferase

O GlcNAcase

O-GlcNAcylation is involved in numerous cellular processes such as … and some … processes

apoptosis, pro oncogenic

… and … often compete for the same or adjacent ser/thr residues on c-Myc TF

phosphorylation and O GlcNAcylation

Threonine-58 Switch

phosphorylation at Thr58 promotes c-Myc … marking the protein for … mediated proteasomal turnover and reduces its …

O-GlcNAcylation at the same Thr58 blocks … protecting c-Myc from … and increases its …

degradation, ubiquitin, stability

phosphorylation, degradation, stability

Serine-62

phosphorylation of … initially stabilises c-Myc and enchances its … activity

however this pSer-62 modification creates the exact structural motif needed by a … enzyme to bind and … Thr 58

once both sites are phosphorylated, the enzyme … removes the … from Ser 62 leaving a singly phosphorylated … residue that is recognised by an enzyme for … degradation

ser 62, transcriptional

kinase, phosphorylate

PP2A, phosphate, thr 58, proteasomal

receptors of the immune system often recognise … structures

glycan

pathogens use … to mask themselves and evade the immune system and disable … …

glycans, immune reactions

which pathogens use carbohydrates for immune evasion

viruses, parasites, bacteria, fungi and tumours

glycans protect the HIV … surface protein responsible for binding … receptors of … cells

GP120, CD4, T

SARS CoV 2 uses its … glycoproteins to bind to human … receptors which allows the virus to enter and infect host cells

spike, ACE2

glycan … is a process where a virus takes control of a host cell’s … machinery to coat its own … proteins with host derived glycans

hijacking, glycosylation, surface

antivirals disrupt glycan … by viruses

hijacking