Part:BBa_K3470007

Circuit

Constitutive Promoter – RBS – MerP – RBS – MerT – RBS – MerE – RBS – MerC – RBS - Double Terminator

Usage and Biology

MerP is the periplasmic component of the mer transport system which helps in the uptake of mercury inside the cell. It binds to a single Hg (II) ion using its two conserved cysteine residues, which define its metal-binding motif. It removes any attached ligands before passing the Hg (II) on to MerT transmembrane protein. It is the most abundantly synthesized protein in the mer operon due to its role in scavenging of Hg (II) in the periplasm. (Steele, R. A., & Opella, S. J.1997).

MerT is a transmembrane protein which receives mercury from MerP, at its first transmembrane helix and transports it into the cytoplasm of the bacterial cell. (T. Barkay et al., 2003). MerE is a transmembrane component of the mer transport system which helps in the uptake of mercury inside the cell. It helps in the transport of organo-mercury compounds. MerC is a transmembrane component of the mer transport system which helps in the uptake of mercury inside the cell. It can function without the help of MerP and has been hypothesized to be required in cases of high mercury concentration. (Sone et al., 2013)

Proposed experimentation

To determine the final transport design, three circuits consisting of a combination of genes among MerP, MerC, MerT and MerE have been proposed. The circuit showing the most effective results must be chosen as the bio-brick for the transport system for our first plasmid.

Circuits we test for the final transport design system:

1. MerP-MerT-MerC-MerE

2. MerC-MerE

3. MerP - MerT – MerE

To test the efficiency and characterize each of the 4 parts separately, experiments must be carried out with each of the parts making use of 2 test circuits and 2 controls.

Circuits:

The final transport design system

Constitutive Promoter- RBS – (The part to be tested, i.e. MerP, MerC, MerT or MerE) -RBS-Double Terminator

Controls:

Final circuit design without the part to be tested

Wild type Escherichia coli DH5alpha

E. coli cells inoculated with methylmercury chloride must be grown for the required amount of time according to the results of the preliminary experiment respectively for the 2 circuits to be tested and 2 controls. The cell suspension must be centrifuged and the mercury concentration in the supernatant for each set should be determined with gas chromatography. Plots of concentration vs time for each of the sets must analyzed to understand the efficiency of the parts in transporting methylmercury.

Expected result:

The most efficient transport system is the final transport circuit design.

If there are two transport system circuits are of similar efficiency, the one with the least expected genetic burden (smaller length) must be selected. The expected result should show the efficiency of MerP, MerT, MerE, MerC all together in transporting methylmercury, which should be higher than the natural transport (without mer operon transporters).

References:

Barkay, T., Miller, S. M., & Summers, A. O. (2003). Bacterial mercury resistance from atoms to ecosystems. FEMS Microbiology Reviews, 27(2–3), 355–384. https://doi.org/10.1016/S0168-6445(03)00046-9

Rossy, E., Sénèque, O., Lascoux, D., Lemaire, D., Crouzy, S., Delangle, P., & Covès, J. (2004). Is the cytoplasmic loop of MerT, the mercuric ion transport protein, involved in mercury transfer to the mercuric reductase? FEBS Letters, 575(1–3), 86–90. https://doi.org/10.1016/j.febslet.2004.08.041

Sone, Y., Nakamura, R., Pan-Hou, H., Itoh, T., & Kiyono, M. (2013). Role of MerC, MerE, MerF, MerT, and/or MerP in resistance to mercurials and the transport of mercurials in escherichia coli. Biological and Pharmaceutical Bulletin, 36(11), 1835–1841. https://doi.org/10.1248/bpb.b13-00554

Steele, R. A., & Opella, S. J. (1997). Structures of the reduced and mercury- bound forms of merP, the periplasmic protein from the bacterial mercury detoxification system. Biochemistry, 36(23), 6885–6895. https://doi.org/10.1021/bi9631632