Previously: Getting things made

Now: getting them where they need to go: Protein Targeting

Translation: Converting nucleotide sequence to amino acid chain

Role of tRNA, base pairing and wobbleRole of ribosome (A, P, E sites)

What happens after proteins are made?

The Protein

What happens to the protein?Folding

Sorting

What happens to the mRNA, the ribosomes & the tRNA?

Reuse

Polysomes

Cell

Neurotransmitters: synthesis and packaging

Where are neurotransmitters/neuropeptides synthesized?

What must happen before theycan be used?

packaging

transportBarriers to packaging

Biological membrane of vesiclePolar nature of neurotransmitter

How are the barriers overcome?

Broad Idea: Perhaps Bipolar is a result of problem(s) getting the transmitters or the receptors to the right place at the right time?

How do we study this?--- examine what ‘should’ happen and look for changes from that ‘standard’

Synaptic vesicles

What are they?

Vesicles are membrane spheres

Neurotransmitters are polar

How do they get in?

How does neurotransmitter packaging occur?

Carrier ProteinsWhy are they needed?How do they work? What kind of energy is needed?

Main Classes: Passive versus Active TransportGoing with or against the flow

Types of active transport: Coupled– ex. symports or antiportsPumps– like STE6, mdr, Ca++ pump (ATP hydrolysis)Light driven pumps (primarily bacterial)

Which class(es) likely to be used in initial packaging of neurotransmitters? In their re-uptake?

Neurotransmitter receptor: synthesis and packaging

Is a neurotransmitter receptor a cytosolic protein?

Cell

Where is it synthesized?How does it get into a membrane? ?

?

Cytosolic vs. Noncytosolic proteins

The catecholamine theory of affective disorder

What sorts of situations could result in this condition?(what would alter the amount of signaling at a synapse?)

1) Don’t make enough neurotransmitter

2) Make it but don’t package it into vesicles or don’t release it correctly

3) Make/ release but receptor not present on post synaptic cellor not functioning correctly

4) Make/ Release/ Receptor there but overactive re-uptakereduces the ‘effective’ amount of neurotransmitter

Importance of specific translocation

>50% of protein made on cytosolic ribosomes are not intended to be used in the cytosol

Must cross between 1 and 3 membranes to reach final destination

Mis-localization can have drastic consequences—disease or death

How does the cell know where to place a protein?

Cellular ‘ZIP code’

Signal Sequences and Signal Patches

Signal sequences

How are these signals used? Necessary and sufficient

Targeting to the ER

TWO methods of targeting to ER

If targeted to the ER where can a protein end up?Main point of entry into the endomembrane systemWhere euk. Membrane proteins become membrane proteins

(except for some mitochondrial and chloroplast proteins)

Minor pathway: Sec-dependent translocationIdentified first in bacterial genetic screens

Post translational