Protein and Enzymes Flashcards
ΔF508 mutation
- most common mutation in cystic fibrosis
- found on the CFTR gene (cystic fibrosis transmembrane regulator, =250,000 bp and 24 exons)
- deletion mutation of 3 nucleotides -> phenylalanine at position 508 lost
- ΔF508-CFTR stays in ER and is targeted for destruction -> only about 2% of needed protein gets to cell membrane
competitive inhibitors
- compete for same site as substrate
- high amounts of substrate will overcome the inhibitor
- Vmax remains the same, but Km is higher
non-competitive inhibitors
- bind to a site different from substrate
- changes the substrate binding site
- substrate can not overcome this change
- Vmax is lower, but Km is the same
Vmax
maximum velocity of a reaction that can occur in presence of enzyme
Km
- michaelis constant
- is the substrate concentration that is found at 1/2Vmax in a michaelis-menten plot
- low Km indicates strong binding affinity
lineweaver burke plot
- turns data from michaelis-menten plot from a hyperbolic shape to a straight line
- x-axis is 1/S and y-axis is 1/V
- the line crosses the y-axis at 1/Vmax
- the line crosses the x-axis at -1/Km
variable changes in competitive inhibition
- Vmax remains the same
* Km increases
variable changes in non-competitive inhibition
- Vmax decreases
* Km remains the same
enzymes
catalytic proteins
defensive proteins
e.g. antibodies
hormonal and regulatory proteins
control physiological processes
receptor proteins
receive and respond to molecular signals
storage proteins
store amino acids
structural proteins
physical stability and movement
transport proteins
carry substances (e.g. hemoglobin)
genetic regulatory proteins
regulate when, how, and to what extent a gene is expressed
secretory proteins are synthesized by
ribosomes bound to the ER (constitutive pathway)
cytoplasmic proteins are synthesized by
free ribosomes in cytoplasm
golgi apparatus
distribution center for proteins and lipids from the ER to vesicles and plasma membrane
endosome
- sorting centers for material from outside the cell or golgi
- sends it to lysosomes for destruction, or back to the membrane/golgi for further use
proteasome
barrel-shaped protein complex that degrades damaged or ubiquitin-tagged proteins
protein folding is
hint when does it happen
co-translational
dominant negative effect
- protein subunits A and B need to form a complex to become active
- if subunit A is misfolded and inactive, but can still join subunit B, then the entire complex becomes inactive
exocytic transport system
- ER -> vesicle -> golgi apparatus -> vesicle -> plasma membrane
- secretory proteins
- membrane proteins
COP II
- coatamer protein II
- expressed on vesicle released from RER that will target the cys golgi (closest to ER)
- KEY: ER -> cys golgi
COP I
- coatamer protein I
- retrograde transport
- if components belonging in ER (ie chaperones) make it to the golgi, the vesicle gets tagged with COP I to go back to ER
- Key: cys golgi -> ER
core glycosylation happens when
co-translational
core glycosylation of protein
- simple high mannose added
- N-glycosylation (n-linked)
- done in ER
complex glycosylation of protein
- done in golgi
* O-glycosylation
constitutive pathway
the default pathway = exocytic pathway
others need regulated pathway, which requires signals
CFTR
- cystic fibrosis transmembrane regulator
- allows for Cl- to exit cells
- important for maintenance of gradients
which amino acid would you not find in an α-helical domain
proline (helix breaker)
sigmoidal curve indicative of
cooperative binding (i.e hemoglobin)
michaelis-menten kinetics
only applies to single subunit enzymes (rare in human body)
