BIOMG 1350 1st Edition Lecture 10 Outline of Last Lecture I. Transporters in the membraneOutline of Current Lecture II. Transport into NucleusIII. Transport into the MitochondriaIV. Transport into ERCurrent Lecture- Both transporters can move ions against the membrane potential. If concentration gradient is larger than membrane potential ions can move against membrane potential.o Every organelle has a specific protein composition. Need the right proteins in therights place. o 2/3 of proteins are found in the cytosol, 1/3 in ERo Signal Sequences are necessary and sufficient to direct a protein to its destination. Signal sequence part of a protein is needed and can target the protein to the correct cell.- Transport into Nucleus:o Go through a nuclear port (no membrane!)o mRNA, tRNA has to get out of the nucleus… DNA polymerase, RNA polymerase, transcription factors, histones (made in cytosol) need to be transported into the cello Small molecules go through, no problem. Larger proteins require a receptor: nuclear import center- NLS will bind protein to nuclear transport receptor and go through the nucleus (active transport). NLS is reused.o Binding of NLS to receptor complex drives receptor into nucleus. Inside, it meets with Ran-GTP bins to receptor and cargo is released. Also induces receptor to leave through nuclear pore. In the cytosol, GTP is hydrolyzed.o The Ran-GEF is in the nucleus, and any Ran-GDP is released and converted to Ran-GTP in nucleus. Ran-GAP in cytosol hydrolyzes GTP and it turns into a Ran-GDP. 95% of Ran is in the nucleus.- Transport into Mitochondria (and chloroplasts):o Double membraneo Similar to transport into nucleusThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Whole protein synthesized in cytosol. Signal sequence meets with receptor and communicates with protein translocater. Must be unfolded by translocater whengoing form nucleus into membraneo Inside, it must refold and signal sequence is cleaved and degraded- Transport into ER:o Proteins from ER Golgi outside the cell (secretory pathway)o Contains a signal sequence. Signal Recognition Particle (SRP) is a ribonuclear particle as it consists of an RNA and 6 associated proteins SRP: mRNA begins translating. Signal sequence is poking out of ribosome. SRP comes and binds it. Signal sequence slows or stops translation. Its binds to SRP receptor on ER. SRP is displaced and recycledand protein goes through translocation channel and is finished translatingin the ER lumen. Translation and translocation are coupled.  This pathway requires: SRP must brings secretory protein to ER, it directs the polypeptide to the translocation channel, it relieves the block in translation Signal peptidase cleaves signal sequence in the ER lumeno For membrane proteins into membrane: When it reaches hydrophobic start-transfer sequence, it stops translocating through translocater membrane. Many membrane proteins contain many stop-transfer and start-transfer sequences. Embedded in primary