Day 10, Lecture 1: Proteins I: Protein structure-Function Flashcards
Amino acids with special features?
- Glycine
- A hydrogen side chain
- small, thus no steric hindrance
- can pack tightly
- Disulfide link
- Crosslink two cysteine (C) groups to join polypeptides together
- Proline
- A secondary amine with a ring; kinks polypeptide chain
The formation of the amide or peptide bond occurs in the
ribosome
The peptide bond can _____ with other peptide bonds and groups
Hydrogen bond
In a polypeptide chain, the only rotation is around the _____. Due to
- Alpha-carbon
- due to steric hindrance and/or interactions between R-groups, only certain favorable angles are allowed between any two residues
Isoforms/isozymes
proteins with distinct sequences that perform the same general function. Optimize performance for functions in other tissues or developmental stages
all peptide bonds are ____ bonding in alpha helix and beta sheets
hydrogen bonding
common amino residues in turns
- glycine, good since no side group
- proline, starts a kink for a tight turn
Motifs
combinations of helix, sheet, etc structures
Denaturing proteins using
- Heat
- pH changes
- Solvent change (turn protein hydrophobic core inside out)
- Toxic ligans (heavy metals can disrupt disulfide links)
Osteogenesis imperfecta
- In some cases, results from a point mutation that changes glycine ot a bulky amino acid that impairs triple helix formation. Strong collagen fibers do not form resulting in “brittle bone disease)
Conformational change of protein can result in change of function such as
- Control activity
- protein off or on depending on a phosphorylation event that changes tertiary structure
- Fine-tune function
- Accommodate several types of molecules
- enzyme can accept a substrate and release a product
- Convey information
- hormone in blood binds to a cell surface receptor that starts a signaling cascade in the cell cytoplasm
Severe hemophilia A
- in some cases, is the result when one of the Arginines at positions 1689 or 372 of Factor VIII is mutated to another residue that cannot be clipped by the protease thrombin; therefore VIII is transformed into the useful form
Sickle Cell anemia A
- Results for a defect in hemoglobin [Hb] beta subunit chain in which glutamic acid #6 has been converted to valine )(HbS) as a result of an A to T point mutation. This forms a “sticky” spot that allows the deoxy form of HbS to polymerize distoring the red blood cell shape
G6PDH deficiency
- Results form numerous missense mutations of this X-linked gene
- results in an unstbale protein with shorter half-life
- therefore, the cells have low amounts of NADPH and glutathione to counteract oxidation products
The critical features of polypeptide structure and of _____ interactions govern folding
bonding interactions
