Difference between revisions of "Part:BBa K249014"

Revision as of 17:03, 31 October 2009

C-terminal YFP --> Tet inverter

Arabinose repressible Tetracycline inversion of YFP with C-terminal Fusion Arganine Tag for targetting into Lumazine Microcompartment. Has a medium RBS and a double terminator.

Sequence and Features

This part was designed as an inversion device for YFP fluorescence. Upon addition of Arabinose the fluorescence of the protein was expected to drop significantly.

Two constructs (EYFP with either N- or C-terminal 10Arg (10R) tags) were characterized by the following procedure, either in the presence or absence of 0.4% w/v arabinose.

Briefly, 5 mL cultures (LB + 10 mg/mL ampicillin, with or without 0.4 % w/v arabinose) were inoculated with 1 mL of previously prepared culture of E. coli DH5α containing the EYFP constructs. After 1 hour growth at 37 °C (with shaking), 1 mL of the culture was harvested. Cells were centrifuged (13500 g, 5 min) and resuspended in 1 mL of either 8 M urea or buffer TAKM7 (50 mM Tris-Cl pH 7.5 at room temperature, 30 mM NH4Cl, 70 mM KCl, 7 mM MgCl2) containing 1 mg/mL lysozyme. Following a 10 min incubation at room temperature, cell debris was removed by centrifugation (13500 g, 5 min). The fluorescence of the resulting clear cell debris was determined using a Varian Cary Eclipse Fluorescence Spectrophotometer in quartz cuvettes, referenced with respect to the background fluorescence of either 8 M urea or buffer TAKM7. The fluorescence of EYFP was excited at 514 nm; the fluorescence emission was measured through 5 nm slits from 520 to 600 nm. The results are summarized below:

Figure 1: Fluorescence of YFP constructs under native conditions. Fluorescence of buffer TAKM7 (black) and DH5α (grey) cell lysates were used as a control and show no significant fluorescence. Cells expressing C-terminal 10R tagged YFP in the absence (dark yellow) or presence (dark green) of arabinose (N-terminal 10R tagged YFP, light yellow and light green without or with arabinose respectively) showed a significant increase in fluorescence after one hour of growth.

Figure 2: Fluorescence of YFP constructs under denaturing conditions. Fluorescence of 8 M urea (black) and DH5α (grey) cell lysates were used as a control and show no significant fluorescence. Only cells expressing C-terminal 10R tagged YFP in the absence (dark yellow) of arabinose showed any fluorescence. Cells expressing C-terminal 10R tagged YFP in the presence (dark green) of arabinose (N-terminal 10R tagged YFP, light yellow and light green without or with arabinose respectively) showed no significant fluorescence under denaturing conditions. 8 M urea buffer had a slight fluorescence when excited at 514 nm.

These results indicate that cells express either N- or C-terminal 10R tagged YFP, as shown by an increase in the fluorescence of cleared cell lysates. This fluorescence can be removed by treating cell lysates with 8 M urea, which would denature the protein, reducing the fluorescence of the lysate. This is demonstrated by a change of 10 fluorescence units between total cellular proteins under native conditions compared to denaturing conditions.