MC3
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Created by:
carifavaro on September 14, 2010
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63 terms
Terms | Definitions |
|---|---|
 noncovalent interactions are | weak but collectively strong enough to define the folded structure of a protein |
| in a folded polypeptide, nonpolar side chains | tend to cluster at the core of the protein and away from the aqueous surrounding, leaving the polar and charged side chains at the surface |
| nonpolar amino acids form the | transmembrane domains of membrane proteins |
| polar and charged amino acids tend to be at the | regions of proteins that are exposed to the aqueous surrounding |
| hydrophobic core regions of polypeptides contain | nonpolar side chains |
| hydrogen bonds in polypeptides | can be formed to the polar side chains on the outside of the molecule |
| secondary structures are | alpha helixes and beta sheets |
| proteisn are synthesized as | polypeptides |
| maturation of proteins involves | correct folding, proteolytic cleavage, chemical modifications, formation of quaternary structures, association with co-factors |
| each step in protein synthesis and maturation can be a target for | control (gene expression) |
| protein degradation is | under tight control |
| chaperones bind to | nascent polypeptides andmaintina a stable unfolded state |
| when synthesis is complete | the chaperons release the polypeptides and allow them to fold correctly |
| chaperones stabilize the | newly synthesized polypeptide |
| chaperones | transport polypeptides |
| chaperons on the other side maintain | the unfolded state until translocation is complete |
| polypepties are allowed to fold when | they reach their final destination |
| what kind of bonds form between adjacent cysteine residues? | disulfide |
| disulfide bonds can link what? | two domains of the same polypeptide or different polypeptide chains |
| elastin fibers | a rubberlike elastic meshwork present in the extracellular matrix of some cell types |
| elastin fibers allow tissues such as skin, arteries and lungs to | stretch and recoil without tearings |
| examples of denaturants | urea or heat |
| denaturants can | unfold a polypeptide by breaking non-covalent interactions between amino acids |
| reducing agents ex. | 2-mercaptoethanol |
| reducing agents are necessary to | break disulfide bonds |
| urea is produced in | the liver of mammals |
| urea helps | excrete ammonia (a toxic metabolic waste product) |
| urea can break | noncovalent interactions between amino acids |
| fibrillar collagens are | the major structural proteins of connective tissues |
| fribrillar collagens are built of | triple helices of procollagen polypeptides |
| TSEs | transmissible spongiform encephalopatheies |
| TSEs are a family of | fatal brain diseases characterized by lesions that appear as small cavities (spongy appearance) |
| Ex. of TSEs | scrapie (sheep), mad-cow disease (cattle), and Creutzfeldt-Jakod disease (CJD), or kuru ("to tremble with fear") (humans) |
| infectious agent in TSEs | prions (proteinaceous infectious particle) |
| TSEs protein only hypothesis | diseases are caused by incorrectly folded versions of the prion protein |
| prions (PrP^sc) are variations of | normal brain protein (PrP^c) |
| a PrP^sc can direct a PrP^sc | to unfold and re-fold into an identical PrP^sc prion |
| new prions can | continue propagation of PrP^sc |
| several strains of prions exist | variations of the prion protein tertiary structure that are also infectious |
| insulin protein | pancreatic hormone that regulates blood glucose levels |
| insulin protein is two chains linked by | disulfide bonds (between closely places cysteines) |
| the insulin protein is originally synthesized as a | single polypeptide preproinsulin |
| insulin protein: connecting polypeptide is removed after | disulfide bonds are made, result = mature insulin |
| regulation of protein activity may occur | at two levels |
| two levels of protein regulation: | regulation of gene expression (determines the amount of protein produced by the cell by limiting transcription and or translation), control of protein function (the protein is synthesized by its activity is restricted according to the needs of the cell |
| the folding of a polypeptide may create a specific ligand... | binding site |
| PKA | promotes glycogen metabolism |
| inactive PKA is a | tetramer: two regulatory subunits bound to two catalytic subunites |
| what activates PKA by binding to the regulatory subunits, causing the release of the catalytic subunits? | cAMP |
| the kinase activity of the released catalytic subunits (in PKA) do what? | phosphorylate multiple effector proteins |
| feedback inhibition: allosteric regulation: | a change in the conformation of a protein that affects its activity due to the binding of regulatory molecule |
| feedback inhibition: the end product of a biosynthetic pathway does what? | inhibits the enzyme that catalyzes the first step of its synthesis, causing the entire pathway to shut down |
| ex. of GTP regulated enzyme activity | the activation of Ran |
| phosphorylation is necessary for what? | the activation or inactivation of many proteins |
| protein kinase enzymes: | transfer a phosphate group from ATP to proteins |
| two types of kinases (depending on target amino acids_ | serine/threonine, tyrosine |
| phosphatases | enzymes that remove phosphate groups from phosphorylated proteins |
| ubiquitin | a small protein that is attached to a target protein and is a label for regulation or destruction |
| the central cylinder of the proteasome contains | the active protease domain |
| ubiquitylation and proteasomal degradation: a ubiquitin ligase enzyme attaches several | ubiquitins to the target protein |
| ubiquitylation and proteasomal degradation: a cap domain of the proteasome (a protease complex) | recognizes the polyubiquitylated target protein |
| ubiquitylation and proteasomal degradation: the ubiquitins are | removed and recycled |
| ubiquitylation and proteasomal degradation: the proteasome degrades the target protein by | sequential ATP-dependent steps |
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