Difference between revisions of "Part:BBa K3470002"

Latest revision as of 10:46, 20 October 2020

MerP, mercuric transport protein periplasmic component

MerP acts like a scavenger of inorganic mercury in cells. It is suggested that it acts in the similar manner are metallothionines in eukaryotic cells which binds to inorganic heavy metals (Hamer DH.,1986). It is expressed in large quantities as compared to other mer operon genes (Hsueh et al., 2017). MerP is also said to increase the local concentration of Hg2+ in the periplasm which can then be given to the inner membrane proteins. MerP did not increase the resistance spectrum when co-expressed with MerC but when co-expressed with merT, MerE or MerF it gave a higher resistance via the increased local concentration (Sone, Y. et al., 2013).

Figure 1: Forms of MerP.

Usage and Biology

In a recent study involving marine mercury resistant strains, it has been shown that strains expressing only MerP and MerT have higher Hg2+ resistance than strains having MerP MerT and MerA showing that the contributions of these genes to mercury resistance is not cumulative. The possible reason for this could be that the burden of a greater number of proteins which reduces the efficiency of the proteins. It also showed that the Minimum inhibitory concentration of strains (marine) containing MerP and MerT is three times higher than strains containing only MerA suggesting that expression of MerP MerT imparts the bacteria with the ability to tolerate Hg2+ (Zhang J. et al., 2020). This result is surprising as in terrestrial and fresh-water strains, MerA is key in ensuring bacterial mercury resistance (Boyd and Barkay, 2012; Chenia and Jacobs, 2017). However, Bioaccumulation capacity of strains containing all three genes was more than the strains containing only MerP and MerT (Zhang J. et al., 2020).

The location of MerP and MerT in the operon are close to each other suggesting that they work co-operatively. In another study, if MerA is not available to the cells, expression of merP and merT can possibly increase the sensitivity of the cells to Hg2+ (Deng and Wilson, 2001). However other studies have shown overexpression of MerP in certain strains increased mercury resistance from 2 mg/L to 6 mg/L (Hsieh et al., 2007). Co-expression of multiple plasmids can also affect the efficiency of the genes (Ding et al., 2019).

There are two heterologous MerP (From gram negative and gram positive) out of which the gram positive merP in the MerP overexpressed strains increased the absorption capabilities of even Cu2+, Cd2+ and Pb2+ by 142, 84 and 33% respectively. The strain carrying Gram-negative merP also increased 47, 55 and 12% for Cu2+, Cd2+ and Pb2+ adsorption, respectively. With regards to Hg, there was a six- to eightfold increase in Hg2+ resistance and an 10% increase in Hg2+ adsorption capacity (Huang C. et al, 2003).

References

Boyd, E., Barkay, T., 2012. The Mercury resistance operon: from an origin in a geothermal environment to an efficient detoxification machine. Front. Microbiol. 3. https://doi.org/10.3389/fmicb.2012.00349.

Chenia, H.Y., Jacobs, A., 2017. Antimicrobial resistance, heavy metal resistance and integron content in bacteria isolated from a South African tilapia aquaculture system. Dis. Aquat. Organ. 126, 199–209

Deng, X., Wilson, D., 2001. Bioaccumulation of mercury from wastewater by genetically engineered Escherichia coli. Appl. Microbiol. Biot. 56, 276–279.

Ding, L.Y., He, N.N., Yang, S., Zhang, L.J., Liang, P., Wu, S.C., Wong, M.H., Tao, H.C., 2019b. Inhibitory effects of Skeletonema costatum on mercury methylation by Geobacter sulfurreducens PCA. Chemosphere 216, 179–185.

Hsieh, J.L., Chen, C.Y., Chang, J.S., 2007. Overexpression of a single membrane component from the Bacillus mer operon enhanced mercury resistance in an Escherichia coli Host. J. Agr. Chem. Soc. Jpn. 71, 1494–1499.

Hsueh, Y.H., Lin, K.S., Wang, Y.T., Chiang, C.L., 2017. Copper, nickel, and zinc cations biosorption properties of gram-positive and gram-negative MerP mercury-resistance proteins. J. Taiwan Inst. Chem. E. 80, 168–175.

Huang, C.C., Su, C.C., Hsieh, J.L., Tseng, C.P., Lin, P.J., Chang, J.S., 2003. Polypeptides for heavy-metal biosorption: capacity and specificity of two heterogeneous MerP proteins. Enzyme Microb. Tech. 33, 379–385. J

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 & pharmaceutical bulletin, 36(11), 1835–1841. https://doi.org/10.1248/bpb.b13-00554

Zhang, J. , Zenga, Y., Liu, B., Deng, X., 2020. MerP/MerT-mediated mechanism: A different approach to mercury resistance and bioaccumulation by marine bacteria. Journal of hazardous material 388 (2020) 122022

Structures:

https://www.rcsb.org/structure/1dvw

https://www.rcsb.org/structure/1AFI

https://www.rcsb.org/structure/2hqi

https://www.rcsb.org/structure/1AFJ

Sequence and Features