regrades need to be typed and turned in next tuesday after class
Post on 21-Dec-2015
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Regrades need to be typed and turned in next TUESDAY after class
X-ray structure of a protein-conducting channel
Secreted Proteins Have a special sequence on them called a
signal sequence, which directs them to Endoplasmic Reticulum
Ribosome brings the half made protein to ER membrane where it must be thread through the membrane
Sec61 is one of these channels that funnels the protein through to the inside of the ER
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BACKGROUND
-how secreted proteins are made-very ordered and controlled
EndoplasmicReticulum
Sec61/SecY
Study Show importance of Sec61/SecY for
protein translocation into ER Use M.jannaschii to determine by X-ray
crystollography at 3.2 A Determine the process of how
translocation is carried out
Mutations Made point mutations in genes of the
subunit to strengthen crystal contact
Hypothesis Proposed a mechanism of the channel
where it opens for polypeptide translocation by displacement of a PLUG
How is this plug unlocked The plug is removed so translocation
can occur from the Signal Sequence that is on the polypeptide
Model from Experimental Work
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Immune System
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Immune Cells Need to be able to present bad guys to
cells that can get rid of them Therefore evolution has created a set of
specially designed proteins for this
MHC class 1 and class 2 MHC1 on all cells. Binds proteins that are
degraded from inside cell and presents them for monitoring
MHC2 present mostly on antigen presenting cells so
OVERALL IDEA, these are great for binding a variety of proteins in order to display on surface
Antibodies
-important for binding antigen so that it may be neutralized andtaken up by cells that eat (macrophage)
Made By B cells Two chains: heavy and light Both have variable and constant regions Variable regions will bind to antigen Change in 1 amino acid of the
sequence is enough for the antibody to be specific for another antigen
How do we get such wide diversity in the body of antibody Have rearrangements of genes Heavy variable chain is encoded by V,
D, J Light chain is encoded by V and J
OVERALL PIC Rearrangement is going to give us the
ability to produce a lot of different antibody in case we come across a antigen of that type
Cell Membranes
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What is in a cell membrane
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What processes occur across a cell membrane Pinocytosis- cell drinking Endocytosis-cell taking up specific
molecules via the molecule binding to a specific membrane protein
Then you have passive diffusion, facilitated diffusion, and active transport
Basic Unit of the bilayer
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Links hydrophillic part to hydrophobic
The phospholipid has double character
-has two parts: Water loving polar head and water hating hydrophobic tail-this is termed an Amphipathic Molecule-when you through in water by itself, it will energetically surround where the heads interact with each other and the tails are hidden from the water and interact with each other- this is called a micelle
How do proteins fit into all this?
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Membrane Proteins need to be designed in a way that allows them to energetically exist in the membrane while still being able to carry out their functions
Kyte-Doolittle plot
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-tells you if you protein of interest crosses the membrane-number of peaks tells you how many times it crosses