Tertiary%20Structure

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Tertiary Structure

• A result of interactions between side (R) chains
  that are widely separated within the peptide
  chain
• Covalent disulfide bonds - between 2 cysteine AA
• Salt bridges - between AA w/ charged side chains
• (acid base AA)
• Hydrogen bonds - between AA with polar R groups
• Hydrophobic attractions - between NP side chains
• Spatial relationship of 2 structures
• Level responsible for 3-D orientation of
  proteins.
• Thermodynamically most stable conformation
  of a protein.
• May have intra-chain and inter-chain linkages

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Tertiary protein structure bonding
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Human insulin, a small two-chain protein
Tertiary structure has both intra-chain
inter-chain disulfide linkages.
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3o protein structure - Non-covalent R group
interactions (a) electrostatic interaction
(b) hydrogen bonding
(c) hydrophobic interaction
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Tertiary structure of the single-chain protein
myoglobin.
found mainly in muscle tissue where it serves
as an intracellular storage site for oxygen
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• Quaternary structure
• Shape or structure from joining more than one
  protein molecule (protein subunits) together to
  make a larger protein complex.
• Same non-covalent bonds as tertiary form
• Electrostatic interactions (Van der Waals)
• Hydrophobic interactions
• Hydrogen bonding
• Quaternary structure is easily disrupted

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Tertiary and quaternary structure of the
oxygen-carrying protein hemoglobin.
When O2 binds to Fe of Heme group, tension on
the molecule pulls an amino acid, which alters
the 3o structure
This in turn affects the 4o structure bonds
Exposes more heme sites - creates greater
affinity for O2
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Protein StructureR eview
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• Review part 1 can you
• List the characteristics of proteins
• Draw the basic structure of amino acids (a.a.)
• Compare contrast structural differences
• between the 4 main classes of a.a.
• Draw a peptide formation between a.a.
• List characteristics of four levels of protein
  
• structure (1o, 2o, 3o, and 4o)
• An interesting game developed at the University
  of Washington that helps solve protein folding
  problems. It gives anyone a chance to participate
  in real solutions to this research. foldit
  instuctions https//www.youtube.com/wat
  ch?vbo99JjnfdA8 Foldit game download
  http//fold.it/portal/

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Types of Proteins

• Two major types - based on structural levels
• Fibrous - peptide chains are arranged in long
  strands/sheets
• Globular - peptide chains are folded into
  spherical/globular shapes

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Fibrous versus Globular protein
Fibrous Proteins  Have fiber-like structures
good structural material. Relatively insoluble
in water. Unaffected by moderate ????????in temp
and pH. Subgroups within this category
include Collagens Elastins the proteins of
connective tissues. tendons and
ligaments. Keratins proteins that are major
components of skin, hair, feathers and
horn. Fibrin a protein formed when blood
clots. Myosin a protein that makes up muscle
tissue
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Globular Proteins  In living organisms Serve
regulatory, maintenance and catalytic roles.
Include hormones, antibodies, and enzymes.
Either dissolve or form colloidal suspensions in
water. Generally more sensitive to temperature
pH change than fibrous protein counterparts.
Examples within this category include Insulin R
egulatory controls glucose levels Hemoglobin Tr
ansport moves O2 around body Myoglobin Storage
stores O2 near muscles Transferrin Transport
moves Fe in blood Immunoglobulins Defense
attacks invading pathogens
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Fibrous structural protein Keratin
Nails Horn Hoof feathers Hair
Keratin structural molecules are normally long
and thin, insoluble in water, very high tensile
strength,and arranged to form fibers.
Composed of long rods, twisted together, laid
down in criss-cross matrix form.
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Keratinized stratified squamous epithelial layer
found only in skin! Dead cell layers at
surface.  Keratin effectively waterproofs cells.
Blocks diffusion of nutrients wastes.
  Provides protection against  friction,
microbial invasion, and desiccation.
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Many cross-links create very little flexibility
horns, claws, hooves, or nails. Fewer
cross-links allows some stretching but returns to
normal wool, skin, and muscle proteins.
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Fibrous structural protein Collagen

• Collagen most abundant protein in human body
• Structural protein
• Major component of the connective tissue
• sheaths muscles attaches them to bone through
  tendons
• or attaches skeletal elements together through
  cartilage

Collagen exists as a molecule that is tightly
coiled about itself forming a secondary triple
coil.
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The molecules bunch together in groups of three,
forming a larger coil (superhelical coil) that
gives collagen fibers their strength in living
tissue.
Tendons
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Collagen structure can be disrupted in diseases
such as scurvy, which is a lack of ascorbic
acid, a cofactor in the hydroxylation of proline
(Hydroxyproline) In addition, collagen structure
is disrupted in rheumatoid arthritis.
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Myosin Actin

• Muscle proteins which allow for contraction of
  the muscle.
• Myosin
• Fibrous tail - two coiled ?-helices
• Globular head - one at the end of each tail
• Actin
• A multimeric protein
• Long fiber of connected globular proteins

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Muscle tissue contracts and relaxes when
triggered by electrical stimuli from brain.
Muscle fibers bundled together make up a single
muscle. Many myofibrils make up each fiber.
Myofibrils have striations, formed by
arrangements of protein molecules.
The protein forms filaments. 2 types of filament
thick thin. Thick filaments contain myosin
thin filaments contain actin, troponin and
tropomyosin.