Protein Structure Flashcards
what are the two types of secondary protein structures
alpha helix and beta pleated sheet
what are the features of the alpha helix
backbone interactions (polypeptide chains twists itself –> spiral; R-chains point outward)
describe secondary protein structure
- folds into regular structures
- results from ‘local’ interactions between amino acids in polypeptide backbone
- involve hydrogen bonds
small changes in amino acid sequence are important because
they can be advantageous and disadvantageous
what are the negatively charged amino acids
aspartic acid, glutamic acid
what are the positively charged amino acids
lysine, arginine, histidine
what are the uncharged polar amino acids
serine, threonine, tyrosine, asparagine, glutamine
what are the non polar amino acids
glycine, alanine, valine, cysteine, proline, leucine, isoleucine, methionine, tryptophan, phenylalanine
a protein consists of
amino group, carboxyl group, peptide bonds, side (R) chains, polypeptide backbone
why are side chains important in polypeptides
provide different functional properties of protein
what is the purpose of the peptide backbone in polypeptides
most important for protein folding by hydrogen bonding
what are the key features of a polypeptide
- peptide backbone
- side chains
how many different amino acids are there
20
how are proteins formed
strings of amino acids called polypeptides
what happens to phospholipids in membranes
heads align (outside) and tails align (inside)
what are the features of the beta-pleated sheet
backbone interactions (proteins backbone folds into zig-zag shape; H bonds form between amino acids in separate areas of a protein)
what is the primary protein structure
amino acid sequence
what is the tertiary protein structure
full three-dimensional structure of protein
- alpha helices, beta sheets, random coils and other loops
- resulting in protein with different domains or regions that have different functions
describe the catabolite activator protein (CAP)
- found in bacteria
- has two domains
- has alpha helices and beta sheets
CAP has two domains. What do they bind to?
- small: DNA
- large: cAMP (changes conformation of CAP, enables it to bind DNA and promote the expression of genes
explain how proteins and ligands bind
- ligand usually binds to amino acid side chains
- needs to fold correctly so that side chains are in proper position and order as unfolded
- ligand sits in binding site through non-covalent bonding to amino acid side chains
what happens when ligands and proteins bind
protein conformation changes, which creates protein activation
what are some advantages of the quaternary protein structure
- construction of large proteins
- proteins gain complex properties (like cooperativity)
what is the quaternary protein structure
association between 2 or more polypeptides in a protein (with identical or different subunits)
what are the types of quaternary structure
globular and fibrous proteins
what is a globular protein and give an example
- has 4 globular subunits
- hemoglobin
what is a fibrous protein and give an example
- has 3 helices supercoiled
- collagen
what is denaturation; what structures relax due to it
loss of proteins activity from broken bonds or deformity (by heat or acidity)
- relaxation of secondary and tertiary structures
why is protein folding critical to its function
can lead to diseases like cystic fibrosis, alzheimer’s, mad cow disease (CJD humans)
what happens to the mutant protein in cystic fibrosis
mutant transport protein cannot fold properly
what happens to the protein in alzheimer’s
amyloid protein forms large insoluble fibres that causes nerve cells to die
what happens to the protein in mad cow disease (CJD)
prion proteins fold incorrectly which damages nerve cells and leads to death
