Molecular Cell Biology Questions

Molecular Cell Biology Questions

  1. a) G protein-coupled receptors (GPCRs), contain transmembrane helices, and their extracellular pats can be glycosylated. GPCRs are divided into two groups that are made up of alpha, beta and gamma subunits. They contain two highly conserved cysteine residues that can form disulfide bonds, to stabilize the receptor structure. They also include seven transmembrane helix proteins (channelrhodopsin) that may contain ion channels within their protein. Its atomic coordinates usually define the protein part of the GPCPs.
  2. b) False. Two main factors determine the sensitivity of a cell towards an agonist peptide, the first being the binding affinity between the peptide agonist and its specific G protein-coupled receptor. Ligand affinity, also known as attraction can be defined as the rate of binding agonist peptide and the G protein-coupled-receptor. It is also determined by ligand/ binding efficacy. Measurement of ligand efficacy has recently become very important in drug discovery and basic biology (Williams and Sewing, 2005). Agonists with positive efficacy, inverse agonists with negative efficacy and neutral antagonists with neutral efficacy all have different effects on the receptor and its associated signaling systems and functions.
  3. Ligand efficacy and binding affinity, as illustrated above are the two requirements for demonstrating and determining specific binding and functional effects of G protein-coupled receptors. Accuracy in the measurement of these two aspects is critical in biology and determining cell activity towards agonists. Binding affinity (the strength of a protein or peptide to bind to its partner, e.g., a drug or inhibitor, is usually measured and reported by the equilibrium dissociation constant (KD). This is used to determine the order of strengths of different bimolecular interactions. The lower the KD value, the higher the binding affinity of the l

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