Week 7_levels of protein structure Flashcards
describe the amino acid structure
central carbon
amino terminal end
carboxyl terminal end
R group
what is an R group?
variable part of amino acids
give amino acids their individual electrochemical characteristics
how many levels of protein structure are there?
4
what is primary structure?
sequence of amino acids in a protein
are R groups part of the peptide backbone?
no
what is secondary structure in a protein?
folding of the protein that is caused by interactions w/in the peptide backone
where do hydrogen bonds form in secondary structure?
form b/n amino hydrogen and carboxyl oxygen atoms
what type of secondary structures are there in proteins?
alpha-helix
beta-pleated sheets (consist of 2 or more hydrogen bonded B-strands)
what is a super secondary structure?
forms when alpha-helices and beta-pleated sheets combine in various ways to form motifs
what are examples of super secondary structures?
B-barrel
B-a-B-unit
what type of bonding holds secondary structures together within the peptide backbone?
H-bonding
what is the tertiary structure?
the entire 3D structure of the entire folded protein
tertiary structure is stabilized by interactions between…
R groups of the amino acids
what are the types of R group interactions?
electrostatic interactions
- H bonding
- ionic bonding
disulfide bridges
Van der Waals interactions
hydrophobic interactions
what are electrostatic interactions?
form b/n R groups to help stabilize tertiary structure
hydrogen bonds b/n R groups
ionic bonds b/n R groups
what are disulfide bridges?
form b/n R groups to help stabilize tertiary structure
cysteines have a sulfhydryl (SH) group
the SH groups of 2 cysteine residues can form covalent bonds called disulfide (S-S) bridges
what are Van Der Waals interactions
help stabilize tertiary structure
a weak attractive force b/n non polar molecules due to charge fluctuations in the electron clouds of atoms
what are hydrophobic interactions?
hydrophobic (water-fearing) R groups will fold to the interior of the protein to avoid contact with aqueous environment
what are protein domains?
functional subunits of a protein
how are protein domains formed?
from a combination of secondary and tertiary interactions
one protein can form multiple ___
domains
any protein that directly binds to DNA (ex. transcription factors) needs a ___
DNA binding domain
activating transcription of gene requires a ___ to recruit ___
transcriptional activation domain (TAD)
RNA polymerase
what is the highest level of structure for a single protein?
tertiary structure
what is quaternary structure?
the interaction of multiple proteins into multi-protein complexes
what is an example of quaternary structure?
hemoglobin protein in RBC’s
what does a hemoglobin consist of?
2 alpha and 2 beta proteins
(4 proteins = tetramer)
what does hemoglobin do?
carries oxygen from lungs to cells of body
proper folding is critical to ___
protein function
what are chaperone proteins?
enzymes that help proteins fold and/or refold
provide an optimal folding environment for other proteins
chaperones are critical to the proper ___ and ___ of most proteins
folding
refolding
___ are unable to function properly and are the cause of certain diseases
misfolded proteins
what is cystic fibrosis?
disease in which abnormally thick mucus blocks airways, causing difficulty breathing
what does the CFTR protein do?
regulates the thickness of mucus
what does a mutation in the CFTR gene do?
blocks the interaction b/n the CFTR protein and its chaperone protein
CFTR protein cannot fold properly and is unable to function
describe relationship between Alzheimer’s disease and protein folding
misfolded Tau proteins and beta-amyloid proteins form protein clumps (tangles and plaques) that collect inside and outside of neurons in the brain and destroy them
protein misfolding is believed to be the primary cause of:
- PD
- HD
- CJD
- many other degenerative and neurodegenerative disorders
therapeutic strategies to reverse ___ or introduce ___ versions of the proteins are an active area of research
reverse misfolding
introduce properly folded versions
