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 wobble Role 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 they can be used? packaging transport Barriers to packaging Biological membrane of vesicle Polar 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 Proteins Why are they needed? How do they work? What kind of energy is needed? Main Classes: Passive versus Active Transport Going with or against the flow Types of active transport: Coupled– ex. symports or antiports Pumps– 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 cell or not functioning correctly 4) Make/ Release/ Receptor there but overactive re-uptake reduces 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 system Where euk. Membrane proteins become membrane proteins (except for some mitochondrial and chloroplast proteins) Minor pathway: Sec-dependent translocation Identified first in bacterial genetic screens Post translational