7.06_2004_PS2key

# D using the specific binding curve below determine

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Unformatted text preview: between total binding and nonspecific binding. d) Using the specific binding curve below, determine the Kd of TGFß57 for high-affinity receptors. Also, find the total number of receptors per cell. *** NOTE: y-axis label: [I125] TGFb-57 Bound (molecules per cell) Answer: The Kd is determined by finding the concentration of TGFß57 at half-maximal binding. Kd= 10nM. The total number of receptors per cell is 19,000. e) You’d now like to determine the sensitivity of these cells to TGFß57. You know that the Kd for binding TGFß57 to its receptor is about 1X10-8 and you know there are a total of 19,000 receptors per cell. You have previously determined that only 13% of the 19,000 receptors must be bound to obtain the maximal cellular response. Determine the TGFß57 concentration needed to induce the maximal response. What would be the concentration of TGFß57 required to obtain maximal response if there were only 5000 receptors per cell, what is the fold difference 7.06 Spring 2004 PS 2 KEY 3 of 7 compared to the normal concerntration you just calculated, and would this make the cell more or less sensitive to TGFß57? Why might a cell want to regulate the number of receptors to a given external signal? Answer: To calculate the concentration of TGFß57 to induce maximal response, you use the equation [L] = Kd/(RT/[RL])-1. [RL] is the number of TGFß57-occupied receptors needed to induce maximal response—which is 13% of 19,000. Plugging all the values in to the equation gives you [TGFß57] = 1X10-9M. If the total number of receptors was reduced to 5000, the [RL] would still be 2470, then [TGFß57] = 5X10-9M—a 5-fold increase in the Kd of TGFß57. This decrease makes the cell less sensitive to TGFß57 because there needs to be a highe...
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## This note was uploaded on 01/23/2012 for the course LSM lsm1301 taught by Professor Seow during the Spring '11 term at National University of Singapore.

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