Journal of Comprehensible Results

Hires SA, Zhu Y, Tsien R (2008)
Optical measurement of synaptic glutamate spillover and reuptake
by linker optimized glutamate-sensitive fluorescent reporters
Proc Natl Acad Sci USA 105:4411-4416

(Translated by Jeff Elhai)

Experiment: Optimization of sensor characteristics

[Need to decrease affinity of glutamate binding protein for glutamate. Site-specific mutagenesis: S73T had KD of 2.5 μM (17x decrease in affinity).
 
[image]
[Picture of GltI bound to glutamate from PDB. Highlight Ser-73.]
[Need to increase response magnitude. Truncate GltI(S73T) on N terminus and C terminus.]
[image]
[Need figure for truncation of sequence. Use graphical convention like that below.]
 
[Measure maximum response to glutamate as in Fig. 1d of all 176 possible truncation combinations. One big winner: 8 amino acids truncated on N terminus, 5 amino acids on C terminus. 44% maximum response to glutamate.

Omit Fig. 2e


Show truncations graphically.
Label color bar with absolute percentages: 7.1% = blue, 44% = red. Draw line from red box to X- and Y-axes
 
Performance of final optimized sensor with the following modifications (as described above): S73T, -8N, -5C.
Optimized range of sensitivity to glutamate.
Optimized range of fluorescent response +/- glutamate.

Change X-axis to 10-9 etc. Draw line from midpoint down to X axis, label KD = 2.5μM.


[Color bar. Erase black. Lines to Y axis. Maximum response = 44%]