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Proteins Structure
Different aspects of protein
| Question | Answer |
|---|---|
| Structural Proteins | serve to maintain shape in biological organisms, such as cytoskeletal proteins, connective tissues, exterior proteins |
| Examples of Structural Proteins | alpha keratin, collagen, fibroin |
| Globular Proteins | Effector molecules, such as enzymes, transport molecules and receptors, transcription factors |
| aAlpha-Keratin Examples | Wool, hair and skin |
| Alpha Keratin Structure | Two right-handed a-helices wrapped around in left-handed superhelix: coiled-coil; 1000A or more, Superhelix constricts a-helix resulting in a 3.5aa/turn, heptad repeat, disulfide bridge |
| Collagen Examples | Most abundant protein in mammals, maintain component of skin, bone, tendon, cartilage, teeth |
| Collagen Structure | Three left-handed helical chains wrap around each other in a right-handed triple helix called tropocollagen 3000A long, 15A wide Glycine appears every three residues in primary structure followed by proline or hydroxyproline |
| Fibroin | Antiparallel beta-sheet structure, covalent bonds run parallel to fiber axis strong but flexible |
| a-helix | Intrastrand H-bonding, R groups positioned outside of helix , 3.6 residues per turn, 1.5A residues per rise, Rise per turn (pitch): 3.6x1.5A=5.4A, the backbone loop closed by an H-bond contains 13 atoms phi=-60 degrees and psi=-45 degrees |
| beta-pleated sheet | composed of beta strands. phi= -135 and psi=135, interstrand hydrogen bonding, strands in beta sheet may be parallel or anti parallel, rise per residue: -3.47 Angstroms for antiparallel strands -3.25 Angstroms for parallel strands |
| beta-turn | four residues are required, allows the peptide chain to reverse direction carbonyl C of one residue is H bonded to the amide proton of a residue three residues away, Proline and Glycine are prevalent in beta turns, |
| Protein folding | The primary force driving protein folding is the packing of hydrophobic residues (excluding water) |
| Variations in secondary structures are primary structures | are driven by hydrogen bonding between elements of the peptide backbone |
| Folding tertiary structure | driven primarily by interactions of the R groups |
| Why is the amino acid glycine found in regions of disallowed space in the Ramachandran plot? | Its small R group is less sterically hindered than other amino acid R groups |
| What is a typical Ramachandran plot used to illustrate | allowable combinations of phi and psi |
| Which of the following is a covalent force that stabilizes tertiary and quaternary structures | disulfide bridges |
| in the presence of a hydrophobic amino acid in a heptad repeat in a-keratin results in what? | a strip of hydrophobic surface area, that when combined with another monomer, results in the formation of a dimer through hydrophobic interactions |
| what type of interaction occurs between the b-pleated sheets of fibroin | van der Waals interactions |
| fibrous proteins, such as collagen, have which one of the following properties? | serve structural roles |
| All of the information necessary for a protein to achieve its intricate architecture is contained within its structure | primary structure |
| the formation of a disulfide bond would be an example of what level of protein structure | both tertiary and quaternary |
| the primary force responsible for protein folding is? | the increase in entropy of water released from hydrophobic residues upon folding |
| The solution to Levinthal's paradox includes | decreased number of available options as the protein folds |
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