Protein Structure, Folding, & Modification Flashcards
Describe the general structure of an amino acid.
All amino acids have a basic amino group, acidic carboxyl group, and R group side chain.
What class of proteins is water-insoluble, rope-like, and built up from repeating elements of secondary structure?
Fibrous proteins
What are some examples of post-translational protein modifications?
Hydroxylation, methylation, acetylation, disulfide bonds, phosphorylation, ubiquitination
Co-translational protein sorting is reserved for proteins produced where?
Proteins produced by bound ribosomes in the RER undergo co-translational sorting. They cross into the ER and then the Golgi for further modification before being secreted from the cell.
What bonds/interactions contribute to the tertiary structure of proteins?
Ionic bonds, disulfide bonds, hydrogen bonds, and hydrophobic interactions between amino acids and their R groups.
Which amino acids have branched chains?
Valine, leucine, isoleucine
What class of proteins are water-soluble, stable structures that generally include all enzymes and regulatory proteins?
Globular proteins
What is the primary structure of proteins?
Sequence of amino acids - determine by DNA
What is the process by which proteins are degraded?
Polyubiquitination - Ubiquitin ligase binds to a degradation signal on the target protein. Multiple ubiquitin tags are necessary for the protein to be recognized by a proteasome for degradation to small peptides.
Alpha helices, beta-pleated sheets, and B-turns (proline only) are part of what protein structure? What bonds stabilize this structure?
Secondary structure stabilized by H bonds
Describe the process of collagen synthesis.
A peptide is hydroxylated in the ER and released from the ribosome where it undergoes glycosylation. Three peptide chains assemble into a triple helix to form procollagen. The procollagen is secreted in vesicles and cleaved outside the cell to form tropocollagen. Tropocollagen is cross-linked outside the cell to form collagen fibrils. Multiple fibrils forms a fiber and multiple fibers form a bundle.
What targets proteins for translation in specific cell regions?
Signal sequence
Which amino acids have a hydroxyl R group?
Serine & threonine
Name the aromatic amino acids.
Phenylalanine, tryptophan, tyrosine (also has an -OH group)
What bonds maintain primary protein structure?
Peptide bonds
Name the smallest amino acids.
Glycine & alanine
Keratin, collagen, and elastin are examples of what class of proteins?
Fibrous proteins
How does a cell respond to unfolded proteins?
When numerous proteins become unfolded, the cell inhibits protein synthesis. The eIF2-GDP complex is phosphorylated and translation of mRNA decreases. Synthesis of chaperone proteins is selectively increased to assist with repair.
What proteins assist with proper protein folding in the ER, cytoplasm, and mitochondria?
Chaperones
What are some examples of globular proteins?
Hemoglobin, Ig, membrane transport proteins, integral membrane proteins, peripheral membrane proteins, glycoproteins, proteoglycans, enzymes
What post-translational modification is required to target proteins for lysosomes?
Phosphorylation of mannose
What are the basic amino acids?
Lysine, arginine, histidine
What are the results of misfolded proteins?
Loss of protein function, protein aggregation, pathway interference
Aggregation of what proteins in neurons leads to cell death and causes Alzheimer’s disease?
Beta-amyloid (plaques, extracellular) & Tau (tangles, intracellular)
