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Bcem 431 > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

Where is calcium concentration highest

Lowest

A

Outside the cell

Inside the cell (has resting (lower) and active phase (higher) )

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2
Q

What is calcium used as

A

A secondary messenger that triggers event in eukaryotic cells

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3
Q

What are the key things in moving calcium

A

PMCA (Ca2+ atpase/ ca2+ pump)

VGCC (voltage gated calcium channel)

RYR/IP3R

CLSQ (calcium sequestering)

SERCA

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4
Q

What is apo- CAM

A

Calmodulin but ca2+ Unbound form

Usually mg bound but look like apo so it’s called apo

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5
Q

What is serca

A

An atpase membrane protein in the SR/ER membrane

It pumps ca2+ into the SR/ER

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6
Q

What is Calsequestrin

A

In the SR/ER lumen

It binds a lot of ca2+ as storage in the SR/ER lumen

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7
Q

What is PMCA

A

a calcium pump in the plasma membrane

It pumps out excess ca2+ from the cell

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8
Q

What does calcium calmodulin do to PMCA and VGCC

A

Binds to their calcium binding domains to

Activate PMCA (to get ca out of cell)

Close VGCC (to make ca not get taken into cell, feedback inhibition)

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9
Q

VGCC is a

A

Heteropentamer

It’s c term inside the cell

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10
Q

VGCC and other ion channels are a target for

A

Calcium channel blocker drugs

To keep ca2+ out

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11
Q

How does ca cam inhibit VGCC

A

Thought feedback inhibition

Binds to the c term cytoplasmic part of the vgcc alpha1 subunit

This binding closes the VGCC channel

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12
Q

What is the inhibition of VGCC called

A

Calcium dependent inactivation (CDI)

Because calcium binds to cam then cam shuts off the channel

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13
Q

What is an isoform

Spliceoform

A

Diff genes

Same gene but spliced diff

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14
Q

How does cam bind to caV1.1 (a skeletal muscle isoform of VGCC)

A

The caV1.1 has a pore that allows ca2+ into the cell

can binds and pulls the two domains of the pore together

Fast inactivation

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15
Q

Binding of ca2+ to cam is

A

Sequenctial

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16
Q

What type of protein is calmodulin

A

And EF hand protein

Had 400 diff target sites (it can do many things)

17
Q

What else can ca cam activate

A

myosin like chain kinase (MLCK)

Bind to the loop in the MLCK c term domain and pulls it off to activate it

Involved in muscle contraction

18
Q

What are EF hand proteins

A

A protein with a EF hand motif (helix loop helix)

Connected by a small beta sheet

binds Ca in the palm of the hand

19
Q

How many EF hand motifs does ca calmodulin have

A

4

They are organized into the n lobe and the c lobe

20
Q

Will position 6 of the EF hand motif ever not be glycine

What’s always in position 1

A

No

Always asp in position 1

21
Q

How does the EF hand bind ca

A

In apo state (no ca bound) the hand is closed

When ca, the hand opens and make a pocket that the substrate (whatever it’s activating) can sit in

22
Q

Once ca bind to to what am happens to the structure

A

In apo it’s disordered, but when ca binds The structures alpha helix forms then it can bind other proteins

23
Q

What do the methionine residues in cam do

How many does it have

A

Make cam sticky so that ca2+ binds (since hydrophobic want to be sheilded)

9 in total (4 in each lobe)

24
Q

Cam is a good

A

Secondary messenger of proteins because it can bind in many ways

25
Q

What is another enzyme that is dependent on ca cam

A

Ca cam dependent protein kinase 1

26
Q

How does ca cam bind to Ca cam dependent protein kinase 1

A

Ca cam dependent protein kinase 1 has a non helical ca-cam binding domain and a helical autoinhibitory domain

This can binding domain has an exposed trp residue

This trp (trp 303) becomes an anchor for the c lobe of calmodulin so it can be pried out of the inhibitory region and be activated

27
Q

What is calcineurin

A

A ca cam dependent phosphotase

Has alpha and beta subunits, a disordered region, and an autoinhibitory peptide

The active site of the A subunit has fe3+ and zn2+

This peptide is pried off by cam, activating the phosphatase

28
Q

What is in the active site of calcineurin

A

Fe3+ and Zn2+

29
Q

What are C2 domains

A

Ca2+ dependent lipid binding domains

Involved in lipid binding

Conserved domains that are attached to the membrane

30
Q

How is PKC (protein kinase c) activated

A

A hormone binds to the GPCR (ex epinephrine)

Signalling pathways make PLC (phospholipase c) cleave PIP2

IP3 (inositol triphosohate) and DAG get formed from PIP2 (they are secondary messengers)

DAG binds to PKC, PKC active only if ca is also bound

IP3 binds to the IP3 receptor (IP3R) in the ER/SR and pumps ca into the cytosol

31
Q

Slide 23 know structur of IP3

A

Okay

32
Q

Role of IP3r

A

In the ER/SR lumen

Release ca into cytosol

33
Q

How is PKC regulated

A

PKC in the cytosol has a autoinhibitory region that needs to be cleaved

PKC has a C2 domain which binds ca2+ and recruits PKC to the membrane

Not active yet, so C1A and C1B binds to DAGS which cleaves off the inhibitory domain

34
Q

What kind of substrates does PKC phosphorylate

A

Ones that are near the membrane

35
Q

How do you make sure that a kinase targets one substrate and not another

A

Change the specificity of the c2 domain to be bound to a different lipid (so not phosserine)

Changes where PKC binds and also what substrates that surround it, this changes it’s substrates

Bcem 431 (26 decks)

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