Biochemistry Chapter 3: Nonenzymatic Protein Function and Protein Analysis Flashcards
What are structural proteins?
Compose the cytoskeleton, anchoring proteins and much of the extracellular matrix.
What is collagen?
STRUCTURAL - makes up most of the extracellular matrix of connective tissue - found throughout the body and is important in providing strength and flexibility
What is elastin?
STRUCTURAL - extracellular matrix, stretches and then recoils like a spring, restoring the original shape of the tissue
What are keratins?
STRUCTURAL - intermediate filament proteins in epithelial cells. Makes up hair and nails. Makes up the mechanical integrity and functions as a regulatory protein.
What is actin?
STRUCTURAL - microfilaments and thin filaments in myofibrils. have a + and - side, allowing them to slide along actin filament
What is tubulin?
STRUCTURAL - makes up microtubules. polarity. Aids in structure, chromosome separation, and intracellular transport
What is myosin?
MOTOR - interacts with actin in myofibril, can also be involved in cellular transport
What are Kinesins and Dyenins?
MOTOR - associated with microtubules
What are characteristics of motor proteins?
- Catalytic activity, acting as ATPases
- Have 1+ heads capable of force generation
What are binding proteins?
Bind a specific substrate, either to sequester it in the body or hold its concentration at steady state.
What are Cell adhesion molecules?
Allow cells to bind to other cells or surfaces
What are 3 types of Cell Adhesion Molecules?
- Cadherins
- Integrins
- Selectins
What are cadherins?
Calcium-dependent glycoproteins that hold similar cells together.
What are integrins?
permit cells to adhere to proteins in the extracellular matrix
What are selectins?
allow cells to adhere to carbohydrates on the surfaces of other cells and are most commonly used in the immune system.
What are antibodies used for?
used by the immune system to target a specific antigen, which may be a protein on the surface of a pathogen or a toxin
What do immunoglobins contain?
They contain a constant region and a variable region; the variable region is responsible for antigen binding.
What are antibodies formed from?
2 identical heavy chains and 2 identical light chains form an antibody. they are held together by disulfide linkages and noncovalent interactions.
What are three types of ion-channels?
Ungated: always open
Voltage-gated: open in a certain range of membrane potential
Ligand-gated: open in the presence of a specific ligand
What are enzyme-linked receptors?
Participate in cell signaling through extracellular ligand binding and initiation of second messenger cascades
What are G protein-coupled receptors?
have a membrane-bound protein associated with a trimetric G protein. They also initiate second messenger systems.
What is the G protein-coupled receptor pathway?
- Ligand binding engages G protein
- GDP is replaced with GTP; the alpha subunit dissociates from the beta and gamma subunits
- The activated alpha subunit alters the activity of adenylate cyclase or phospholipase C
- GTP is dephosphorylated to GDP; the alpha subunit rebinds to the beta and the gamma subunits.
What is electrophoresis?
uses a gel matrix to observe the migration of proteins in response to an electric field.
What is Native PAGE?
Maintains protein’s shape, but results are difficult to compare because the mass-to-charge ratio differs for each protein.
What is SDS-PAGE?
Denatures the protein and masks the native charge so that comparison of size is more accurate, but the functional protein cannot be recaptured from the gel.
What is isoelectric focusing?
Separates proteins by their isoelectric point; the protein migrates toward an electrode until it reaches a region of the gel where pH = pI of the protein.
What is chromatography?
separates protein mixtures on the basis of their affinity for a stationary phase or a mobile phase.
What is column chromatography?
uses beads of a polar compound, like silica or alumina, with a nonpolar solvent
What is Ion-exchange chromatography?
Uses a charged column and a variable saline eluent.
What is size-exclusion chromatography?
Relies on pourous beads. Larger molecules elute first because they are not trapped in the small pores.
How is protein structure primarily determined?
through X-ray crystallography, NMR can also be used
How can amino acid composition be determined? sequencing?
Comp = simple hydrolysis Seq = Edman degradation
How can activity levels of protein be determined?
- Watch for color change
- BCA assay, lowry reagent assay and Bradford protein assay (most common)
