Nonenzymatic Protein Function and Protein Analysis Flashcards
Structural Proteins definition and examples
Compose the cytoskeleton, anchoring proteins, and
much of the extracellular matrix. The most common
structural proteins are collagen, elastin, keratin, actin,
and tubulin. They are generally fibrous in nature.
Motor Proteins and examples
Have one or more heads capable of force generation
through a conformational change. They have catalytic
activity, acting as ATPases to power mvmt. Common
applications include muscle contraction, vesicle mvmt
within cells, and cell motility.
Give Examples of Motor Proteins
myosin, kinesin, and dynein.
Binding Proteins
Bind a specific substrate, either to sequester it in the
body or hold its concentration at steady state
G Protein-Coupled
Receptors
GPCR has a membrane-bound protein called the GProtein
(a, b, y subunits). The 1st messenger ligand
initiates the 2nd messenger and the cascade response
Cell adhesion molecules
Allow cells to bind to other cells or surfaces.
Cell adhesion molecules: Cadherins
Calcium dependent glycoproteins that
hold similar cells together.
Cell Adhesion
Molecules (CAM): Integrins
Have two membrane-spanning chains and
permit cells to adhere to proteins in the extracellular
matrix.
Cell Adhesion
Molecules (CAM): Selectins
Allow cells to adhere to carbohydrates on
the surfaces of other cells and are most commonly
used in the immune system.
Antibodies
Immunoglobulins, Ig. Used by the immune system to
target a specific antigen, which may be a protein on
the surface of a pathogen or a toxin. The variable
region is responsible for antigen binding.
Electrophoresis
Uses a gel matrix to observe the migration of proteins in
responses to an electric field
Native PAGE:
: Maintains the protein’s shape, but results are difficult to
compare because the mass / charge ratio differs for
each protein.
SDS-PAGE
Denatures the proteins and masks the native charge so
that comparison of size is more accurate, but functional
protein cannot be recaptured from the gel.
Isoelectric
Focusing:
Separates proteins by their isoelectric point (pI); the
protein migrates toward an electrode until it reaches a
region of the gel where pH = pI of the protein
Chromatography
Separates protein mixtures on the basis of their affinity
for a stationary phase or a mobile phase
Column
Chromatography
Uses beads of a polar compound (stationary phase) with
a nonpolar solvent (mobile phase).
Ion-Exchange
Chromatography
Uses a charged column and a variably saline eluent.
Size-Exclusion
Chromatography
Relies on porous beads. Larger molecules elute first
because they are not trapped in the small pores.
Affinity
Chromatography
Uses a bound receptor or ligand and an eluent with free
ligand or a receptor for the protein of interest.
Ungated ion Channels
Always open
Voltage-Gated Channels
Open within a range of
membrane potentials.
Ligand-Gated Channels:
Open in the presence of a
specific binding substance, usually a hormone or
neurotransmitter.
Enzyme-Linked
Receptors
Participate in cell signaling through extracellular ligand
binding and initiation of 2nd messenger cascades
How is the protein structure determined?
Primarily determined through x-ray crystallography
after the protein is isolated, although NMR can also be
used.
How is an amino acid sequence determined?
Edman degradation
How is protein concentration determined?
Determined colorimetrically, either by UV
spectroscopy or through a color change reaction.
Bradford Assay, BCA Assay, and Lowry Reagent Assay
each test for protein and have different advantages
and disadvantages. The Bradford Protein Assay is most
common. It uses a color change from brown-green –>
blue.
How to determine absorbance of a protein?
Beer-lambert law: Absorbance = eCl
e= extinction coefficient C=concentration
l = path length in cm
