Download Protein Folding and Membrane Structure

Proteins and Membranes
How the Parts of Cells are
Put Together
Review of Last Time….
Where is the Genetic Material Located?
In the mitochondria
In the nucleus
Distribution of Genetic Material
How the DNA is Packaged
Genes Can Be Made in Two Directions
Basic Gene Regulation
Initiation of Transcription
mRNA Structure is Different in
Eucaryotes versus Procaryotes
There are Multiple Levels at which
Proteins Production is Controlled
Sequence of Protein Dictates
its Folding Pattern
Primary Protein Sequence
Secondary Protein Structure is
Due to Hydrogen Bonding
Beta sheet
Hydrogen bonding
Alpha helix
Higher-order Structure of Proteins
Disulfide bonds are also
important in protein structure
Proteins Can be Built from
Modular “Domains”
Genes can evolve by
the combining and
swapping of domains
Proteins Can Assemble into
Higher-order Structures
Example:Intermediate Filaments
Intermediate filaments are structural elements
within eucaryotic cells
Assembly of Intermediate Filaments
Tubulin Assembly
Microtubule Dynamics
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Focal Adhesion Structure
Focal Adhesions
The Cell as a Factory
Energy production
Project
management
Data retrieval
Data storage
Data management
Data processing
Shipping
Waste management
Routing
Facilities
Transportation
Communications
Manufacturing
Packaging
Machine shop
Bacteria Also Have Complex Structure
Eucaryotic Cells Distinguished by Complex
Membrane-bound Compartments
Proteins Must Be Sorted to the Correct
Location to do Their Jobs
CYTOSOL
NUCLEUS
Proteins are made on ribosomes,
which are in the cytosol
PEROXISOME
MITOCHONDRIA
PLASTIDS
ENDOPLASMIC RETICULUM
SECRETORY
VESICLES
ENDOSOMES
CELL SURFACE
= gated transport
= transmembrane transport
= vesicular transport
GOLGI
LYSOSOMES
KEY:
The Golgi Apparatus Packages
Proteins for Export
Routes of Protein Export
High mannose
trimmed back
High mannose
CHO added
Membranes are Made From Lipids
• Can form bilayer structure spontaneously
• Considered the solvent for integral
membrane proteins
• Serve as substrates for biochemical and
signaling reactions
Lipids are Amphipathic
Diverse Lipid Structures
Phospholipids
Glycolipids
Fluid Mosaic Model of Biological Membranes
• Singer and Nicolson (1972) synthesized a variety of results that
implied the unit membrane is a fluid and contains proteins as
integral components
• Today we recognize fluidity restrictions and local membrane
domains (Domain Mosaic Model)
Membrane Proteins
About 1/3 of higher eucaryotic gene products are membrane proteins
Proteins Contain Signals Necessary to
Reach the Correct Location
Membrane Transport:
Carriers, Pumps, and Channels
•
•
Carriers and channels facilitate diffusion across membranes
Carriers can also be involved in active transport, which requires
energy expenditure either directly or indirectly
Membrane Ion Pumps
• Couple the energy released by ATP hydrolysis to the formation of
transmembrane electrochemical gradients
• Examples, H-Pump from Neurospora crassa, Ca-Pump in sarcoplasmic
reticulum, Na,K-ATPase
Structure of Neurospora H-ATPase at 8 Å
Proposed Gating Transition
Web Links
http://web.mit.edu/esgbio/www/7001main.html
http://www.library.csi.cuny.edu/~davis/Bioinfo_326/main.html
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html
http://www.accessexcellence.org/RC/