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PARP 2019 > Proteins 3 > Flashcards

Proteins 3 Flashcards

1
Q

What is an isoform? Give examples.

A

A specific form of a protein that belongs to a group with similar structures.

Lactate dehydrogenase (LDH) can exist as a homotetramer or a heterotetramer (M and H)

H4, H3M1, H2M2, H1M3, and M4 are all isoforms of Heart tissue.

Isoenzymes/Isozyme are the same thing, but refer to enzymes

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2
Q

How can a clinical test based on concentrations of a particular isoform be used for myocardial infarctions?

A

Certain isoforms for some proteins can exist in varying concentrations depending on developmental stages.

H4 heart tissue is predominant in adult hearts. If it is found in the blood, a myocardial infarction (heart attack) is likely.

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3
Q

Describe acetylation. What enzyme catalyzes acetylation?

What enzyme catalyzes deacetylation (opposite)?

A

Adds acetyl to certain lysine residues on tail of Histone H3

Acetylation reducues affinity of H3 to DNA, Site opens up and become available for chromatin remodeling (euchromatin)

Deacetylase catalyzes the removal of acetyl groups (closes back up)

The purpose of this modifier is to control gene expression.

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4
Q

Describe methylation. types?

A

There are 2 types: O-linked and N-linked methylation.
It is the addition of methyl to a compound.

methylation of AA with distal amino (N-linked) (Arg, Lys) or carboxyl (O-linked) (Asp, Glu) groups.

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5
Q

Describe hydroxylation (add more to this after reading)

A

A transcriptional modifier that adds a hydroxyl group into a compound.

Purpose:

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6
Q

Describe carboxylation. What cofactor is needed? Give an example of its use.

A

A transcriptional modifier that adds a carboxyl group va addition of CO2.

MUST have K+ as a cofactor to occur

ex: Carboxylation of glutamic acid is often seen in blood clotting factors (Gla proteins)

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7
Q

Describe lipidation. What are the 3 types of anchorage/attachment?

A

A transcriptional modifier that is used to covalently anchor soluble proteins to membrane surfaces.

Some cell surface proteins are attached to outer membrane via GPI anchors.

The 3 types include:
Acylation (myristoyl or palmitoyl groups)
Prenylation (farnesyl or geranygeranyl)
glycosylphosphatidylinositol (GPI) anchor

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8
Q

Describe phosphorylation (Pophotases and Kinases)

A

Phosphotases: A transcriptional modifier that catalyze the addition of a phosphate group

Kinases: A transcriptional modifier that catalyzes the transfer of a phosphate group from high energy ATP to another molecule

Purpose is to turn up/down activity via phosphate group movement.

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9
Q

Describe glycosylation. Types? Carried out by what enzymes? Usually present on what kind of proteins?

A

Glycosidic addition of carbohydrate chain to a protein.

Can be O-linked or N-linked glycosylation.

Carried out by specific Glycosyltransferases.

Present only on secreted proteins (TSH, LSH,) or the extracellular face of membrane bound proteins.

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10
Q

What is an integral membrane protein?

A

An integral membrane protein is a protein permanently attached to a membrane.

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11
Q

What is a peripheral membrane protein?

A

A peripheral membrane protein adheres briefly to a membrane.

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12
Q

How are integral membrane proteins oriented in a membrane?

A

three parts: extracellular, membrane-spanning, and cytoplasmic

Membrane-spanning portion may consist of one or more a-helices (glycophorin) or a b-barrel (porins)

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13
Q

How can amino acid sequences be used to predict transmembrane regions of these proteins?

A

Can predict which segment is membrane-spanning by constructing a “hydrophathy plot”

This just means we look at the residues, and based on their properties we can assume they locate into certain parts of the membrane

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14
Q

Describe signalling through G-proteins via G-protein coupled receptors binding to a hormone/ligand.

A

.

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15
Q

How are secreted and membrane-bound proteins secreted through the cell to various compartments (sorting or targeting)?

A

.

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16
Q

What is a chaperone protein? Give examples

A

.

17
Q

Name common protein denaturants.

A

.

18
Q

How is a proteins function tied to its structure?

A

.

19
Q

How does an amino acid sequence determine the tertiary structure?

A

.

20
Q

Describe the protein folding/unfolding process

A

.

21
Q

list and describe amyloid diseases related to misfolded proteins (do these from slide as you go)

A

.

22
Q

What is the purpose of post-translational modification?

A 
Fine tune the properties of a protein by introducing:
local charges
hydrophobic groups
hydrophilic groups
antigenic properties
23
Q

Are post-translational modifications spontaneous?

A

No, they are all due to specific enzymatic activity.

exception: non enzymatic glycation of hemoglobin to form HbA1c

24
Q

What isoform of hemoglobin is used for diabetic blood sugar testing?

A

HbA1c can be used to test for long term blood glucose levels. Glycation depends on blood glucose levels.

Good for up to 3 months of data because red blood cells live about that long.

25
Q

What are the physiological roles of glycosylation in glycoproteins?

A

Proper folding of transmembrane protein, structural stability, recognition of cell adhesion

26
Q

Where do the specific antigen factors of blood groups come from?
Is there a common antigen between blood groups?

A

Glycosyltransferases add carbohydrates/sugars to erythrocyte proteins and lipids on membrane (O, A, B, AB) that act as antigens.

All blood groups have the common structure for O antigens, but A and B have an extra monosaccharide.

27
Q

Heterotrimeric G-proteins are lipidated via what groups? What do these groups allow them to do?

A

lipidated via myristoyl and geranylgeranyl groups, respectively.

Allows them to translocate along the cytoplasmic face of the membrane

28
Q

The three forms of lipidation can each respectively attach to what groups?

A

Acyl group can be attached to N-terminal glycine

Prenyl group via C-terminal cysteine

GPI anchor to C-terminus

29
Q

How do the membrane transport proteins work? (Ion channels, Pumps, and Transporters.)

A

Pumps use energy released from ATP hydrolysis to move specific ions against an electrochemical gradient (active transport)

Channels permit the movement of ions down their electrochemical gradient. Can be nongated or gated. (passive transport)

Transporters facilitate movement of specific small molecules or ions:
Uniporter: brings a single type of molecule down its gradient

 Symporter: Bring in one type of molecule powered by the movement of another ion/molecule down its gradient into the cell.

 Antiporter: Bring one thing in by pushing out another

PARP 2019 (7 decks)

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