Review session: tonight at 7 pm in Lawrence 115
First midterm: next Wednesday (10/18) 7 pm in MacKenzie 240C
Midterm will cover up through the end of this week (lectures 1-9, homework 1-3, lab 1-3).
If you've talked to me about an alternate exam location/time, please talk to me after class
Receptors have almost identical steroid binding pockets
How do almost identical receptors distinguish between almost identical steroids?
Binding specificity is discrimination between steroids.
Specificity is determined by:
Biochemists use dissociation constants ($K_{D}$) to measure binding affinity
$ML \rightleftarrows M + L$
$M$ is macromolecule (protein)
$L$ is ligand (small molecule)
We can measure $K_{D}$ by following $\theta$ versus $[L]$
$K_{D} = \frac{[M][L]}{[ML]}$
$[ML] \times K_{D} = [M][L]$
$[ML] = \frac{[M][L]}{K_{D}}$
$\theta = \frac{[ML]}{[M] + [ML]}$
$\theta = \frac{[M][L]/K_{D}}{[M] + [M][L]/K_{D}}$
$\theta = \frac{[L]/K_{D}}{1 + [L]/K_{D}}$
$\theta = \frac{1}{1 + K_{D}/[L]}$
The $K_{D}$ is the concentration of $L$ at which $\theta = 0.5$.
Chen et al. (2004) JBC 279(32):33855-33864Steroids have only a small range of blood concentrations
ER responds to physiological concentrations of estrogen but not testosterone
Is one hydrogen bond, in principle, enough to explain the difference in bindng?
Summary
Review session: tonight at 7 pm in Lawrence 115
First midterm: next Wednesday (10/18) 7 pm in MacKenzie 240C
Midterm will cover up through the end of this week (lectures 1-9, homework 1-3, lab 1-3).
If you've talked to me about an alternate exam location/time, please talk to me after class