3-D Structure of Proteins Flashcards
What is the primary organization of proteins?
Amino acid sequence + disulfide bonds
What is the secondary organization of proteins?
Regular recurring arrangements of adjacent amino acids
What is the tertiary organization of proteins?
Arrangement of the total protein, the complete 3D structure
What is the quaternary organization of proteins?
The arrangement of multiple protein subunits
When a protein is denatured, what bonds aren’t broken?
Disulfide bonds
Peptide bonds
What is a domain, with regards to proteins?
A contiguous region with a distinct function
What are some examples of protein domains?
DNA binding
Transmembrane
Calcium binding
Peptide bonds and disulfide bonds are both which type of bond?
Covalent
Peptide bonds are ___ and ___.
Planar and rigid
Which amino acid acts as the “oxidative stress sensor”?
Cysteine
What are the 3 major secondary structure types in proteins?
Alpha helix
Beta pleated sheet
Beta turn
In alpha helices, where do the peptide bonds align?
Along the long axis
In alpha helices, where are the R groups?
Sticking out of the sides
Each turn in alpha helices uses about how many amino acids?
About 3.6
How are alpha helices stabilized?
Lots of hydrogen bonding
Which amino acid is generally a “helix breaker”?
Proline
What things are alpha helix destabilizers?
- A string of several basic or acidic amino acids
- A string of several amino acids with bulky side groups
- Amino acids 3-4 residues apart which cannot interact
- Proline residues
- A string of glycine residues
How are beta pleated sheet chains arranged?
May be in parallel or anti-parallel fashion
What is beta pleated sheet?
Extended arrangement of polypeptides
What hold the adjacent chains together in beta pleated sheet?
Hydrogen bonds
Beta turns contain which amino acid?
Proline
In which conformation is proline found in beta turn?
The cis conformation
What converts proline from the trans to the cis conformation?
Proline isomerase
What are the two major groups of protein tertiary structure?
Globular
Fibrous
Are fibrous proteins primarily water soluble or insoluble?
Water insoluble
Which group of proteins (globular or fibrous) are structural proteins?
Fibrous proteins
How are fibrous proteins usually arranged?
In long chains or sheets
What are classic examples of right-handed alpha helix?
alpha and beta keratin
Where is alpha and beta keratin found?
Hair
Nails
Feather
etc.
What type of amino acids are found in alpha and beta keratin?
Many hydrophobic amino acids
What is a protofilament?
2-stranded superhelix
How do alpha and beta keratin crosslink?
Via disulfide links
To create a perm, what bonds are broken and then reformed?
Disulfide bonds
How many types of keratin are there in the skin?
At least 18
Cytokeratins can be diagnostic for what?
Tumors
Most enzymes and protein hormones are what type of protein?
Globular proteins
Which structure is more complex in globular proteins than in fibrous proteins?
Secondary structure
What shape do globular proteins take on, due to the multiple arrangements of folding?
“spherical”
What are the 4 bond types found in the tertiary structure?
Hydrogen bonds
Ionic bonds
Hydrophobic interactions
Van der Waals forces
What occurs in an H+ bond?
An electronegative atom (Usually O or N) acts as a Hydrogen acceptor
What is an ionic bond?
Attraction between oppositely charged atoms
What are hydrophobic interactions?
Forces that hold nonpolar regions together
What are van der Waals forces?
Weak attractions resulting from transient dipole formation
What proteins assist in folding or assembling subunits of a new protein?
Chaperone proteins
What are the most famous chaperone proteins?
Heat shock proteins
What causes prion diseases?
Improper folding of PrP protein
What is Scrapie?
Spongiform encephalitis found in sheep
What is kuru?
Human spongiform disease found in the Fore tribe of New Guinea
What is Creutzfeldt-Jacob disease?
Sporadic, hereditary degenerative neurologic disease
What causes cystic fibrosis?
Defective protein folding
Which protein is missing an amino acid leading to cystic fibrosis? Which amino acid is missing?
Chloride channel protein is missing Phe-508
When is quaternary structure found in proteins?
Only if the protein has more than one protein subunit
What are some huge proteins with quaternary structure?
Pyruvate dehydrogenase
Ribosomes
RNA polymerase
What is the best way to study protein structure?
Via x-ray crystallography
What things will denature the secondary-quaternary structure of proteins?
Heat
pH extremes
Detergents
Organic solvents (alcohol, acetone, urea)
How can the primary protein structure be broken?
Boiling in a strong acid or base
What things can cleave proteins at specific dipeptide sites?
Proteases
What chemical can be used to reduce disulfide bonds?
Beta-Mercaptoethanol (BME)
Tertiary structure is dictated by what?
Primary structure