Topic
Ars operon
About: Ars operon is a research topic. Over the lifetime, 150 publications have been published within this topic receiving 13530 citations.
Papers published on a yearly basis
Papers
TL;DR: The first bacterial metallothionein cation-binding proteins, which by definition is a small protein that binds metal cations by means of numerous cysteine thiolates, has been characterized in cyanobacteria.
Abstract: Bacterial plasmids encode resistance systems for toxic metal ions including Ag+, AsO2-, AsO4(3-), Cd2+, CO2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, Sb3+, TeO3(2-), Tl+, and Zn2+. In addition to understanding of the molecular genetics and environmental roles of these resistances, studies during the last few years have provided surprises and new biochemical mechanisms. Chromosomal determinants of toxic metal resistances are known, and the distinction between plasmid resistances and those from chromosomal genes has blurred, because for some metals (notably mercury and arsenic), the plasmid and chromosomal determinants are basically the same. Other systems, such as copper transport ATPases and metallothionein cation-binding proteins, are only known from chromosomal genes. The largest group of metal resistance systems function by energy-dependent efflux of toxic ions. Some of the efflux systems are ATPases and others are chemiosmotic cation/proton antiporters. The CadA cadmium resistance ATPase of gram-positive bacteria and the CopB copper efflux system of Enterococcus hirae are homologous to P-type ATPases of animals and plants. The CadA ATPase protein has been labeled with 32P from gamma-32P-ATP and drives ATP-dependent Cd2+ uptake by inside-out membrane vesicles. Recently isolated genes defective in the human hereditary diseases of copper metabolism, Menkes syndrome and Wilson's disease, encode P-type ATPases that are more similar to the bacterial CadA and CopB ATPases than to eukaryote ATPases that pump different cations. The arsenic resistance efflux system transports arsenite, using alternatively either a two-component (ArsA and ArsB) ATPase or a single polypeptide (ArsB) functioning as a chemiosmotic transporter. The third gene in the arsenic resistance system, arsC, encodes an enzyme that converts intracellular arsenate [As (V)] to arsenite [As (III)], the substrate of the efflux system. The three-component Czc (Cd2+, Zn2+, and CO2+) chemiosmotic efflux pump of soil microbes consists of inner membrane (CzcA), outer membrane (CzcC), and membrane-spanning (CzcB) proteins that together transport cations from the cytoplasm across the periplasmic space to the outside of the cell. Finally, the first bacterial metallothionein (which by definition is a small protein that binds metal cations by means of numerous cysteine thiolates) has been characterized in cyanobacteria.
1,321 citations
TL;DR: While the overall schemes for arsenic resistance are similar in prokaryotes and eukaryotes, some of the specific proteins are the products of separate evolutionary pathways.
798 citations
TL;DR: The DNA sequencing and protein crystal structures have established the convergent evolution of three classes of arsenate reductases, which involve three cysteine thiols and S-As bond intermediates, so convergence evolution to similar mechanisms has taken place.
Abstract: Arsenic compounds have been abundant at near toxic levels in the environment since the origin of life. In response, microbes have evolved mechanisms for arsenic resistance and enzymes that oxidize As(III) to As(V) or reduce As(V) to As(III). Formation and degradation of organoarsenicals, for example methylarsenic compounds, occur. There is a global arsenic geocycle, where microbial metabolism and mobilization (or immobilization) are important processes. Recent progress in studies of the ars operon (conferring resistance to As(III) and As(V)) in many bacterial types (and related systems in Archaea and yeast) and new understanding of arsenite oxidation and arsenate reduction by respiratory-chain-linked enzyme complexes has been substantial. The DNA sequencing and protein crystal structures have established the convergent evolution of three classes of arsenate reductases (that is classes of arsenate reductases are not of common evolutionary origin). Proposed reaction mechanisms in each case involve three cysteine thiols and S–As bond intermediates, so convergent evolution to similar mechanisms has taken place.
751 citations
TL;DR: A mechanism of arsenite [As(III)]resistance through methylation and subsequent volatization is described, and this microbial-mediated transformation is proposed to have an important impact on the global arsenic cycle.
Abstract: In this article, a mechanism of arsenite [As(III)]resistance through methylation and subsequent volatization is described. Heterologous expression of arsM from Rhodopseudomonas palustris was shown to confer As(III) resistance to an arsenic-sensitive strain of Escherichia coli. ArsM catalyzes the formation of a number of methylated intermediates from As(III), with trimethylarsine as the end product. The net result is loss of arsenic, from both the medium and the cells. Because ArsM homologues are widespread in nature, this microbial-mediated transformation is proposed to have an important impact on the global arsenic cycle.
641 citations
TL;DR: Yeasts extrude arsenite using Acr3p, a plasma membrane carrier protein, or sequester it in vacuoles as the glutathione conjugate using Ycf1p, an ABC transporter.
363 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 4 |
| 2020 | 3 |
| 2019 | 6 |
| 2018 | 5 |
| 2017 | 4 |
| 2016 | 8 |