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merT, mercuric transport protein

Overview

Transmembrane mercuric binding gene merT (0.3Kb) encodes MerT, which transports Hg(II) species from the periplasm through the membrane. MerT and gene merT are highlighted in purple in Figure 1. The lower part of the Figure 1 shows the arrangement of mer genes in the operon, and merT is located upstream of merP, another gene that encodes a mercury transport protein.

Figure 1. Model of transmembrane mercuric binding protein MerT. The symbol • indicates a cysteine residue. RSH indicates cytosolic thiol redox buffers such as glutathione. Figure 1 shows the interactions of MerT, in purple, with mercury compounds and other gene products of mer operon. (This figure is adapted from "Bacterial mercury resistance from atoms to ecosystems". Reference: T. Barkay et al. FEMS Microbiology Reviews 27 (2003) 355-384.)

merT is found in the Serratia marcescens plasmid pDU1358 on the other side of the bidirectional promoter opposite of merR. It is 351 base pairs long and it codes for a mercuric transport protein.

Structure

Structure of merT can not be obtained due to the difficulty in obtaining the crystalline structure of a transmembrane protein.

Mechanism The transport mechanism of ionic mercury from the bacterial cell periplasm to cytosplasm is not completely understood. However, it is thought that in cooperation with merP, a periplasmic mercury binding protein, Hg 2+ is transferred from merP to the first of the three transmembrane helices onto two cysteines within merT.

Sequence and Features