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Titolo:
NEWER SYSTEMS FOR BACTERIAL RESISTANCES TO TOXIC HEAVY-METALS
Autore:
SILVER S; JI GG;
Indirizzi:
UNIV ILLINOIS,COLL MED,DEPT MICROBIOL & IMMUNOL,MC790,BOX 6998 CHICAGO IL 60680
Titolo Testata:
Environmental health perspectives
, volume: 102, anno: 1994, supplemento:, 3
pagine: 107 - 113
SICI:
0091-6765(1994)102:<107:NSFBRT>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
STAPHYLOCOCCUS-AUREUS PLASMID-PI258; PROKARYOTIC METALLOTHIONEIN LOCUS; ALCALIGENES-EUTROPHUS CH34; COPPER RESISTANCE; CADMIUM RESISTANCE; PSEUDOMONAS-SYRINGAE; NUCLEOTIDE-SEQUENCE; ESCHERICHIA-COLI; CANDIDATE GENE; MENKES DISEASE;
Keywords:
ARSENIC; BACTERIAL PLASMIDS; CADMIUM; COPPER; MERCURY; METALLOTHIONEIN; METAL RESISTANCES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
45
Recensione:
Indirizzi per estratti:
Citazione:
S. Silver e G.G. Ji, "NEWER SYSTEMS FOR BACTERIAL RESISTANCES TO TOXIC HEAVY-METALS", Environmental health perspectives, 102, 1994, pp. 107-113

Abstract

Bacterial plasmids contain specific genes for resistances to toxic heavy metal ions including Ag+, AsO2-, AsO43-, Cd2+, Co2+, CrO42-, Cu2+,Hg2+ Ni2+, Pb2+, Sb2+, and Zn2+. Recent progress with plasmid copper-resistance systems in Escherichia coil and Pseudomonas syringae show asystem of four gene products, an inner membrane protein (PcoD), an outer membrane protein (PcoB), and two periplasmic Cu2+-binding proteins(PcoA and PcoC). Synthesis of this system is governed by two regulatory proteins (the membrane sensor PcoS and the soluble responder PcoR, probably a DNA-binding protein), homologous to other bacterial two-component regulatory systems. Chromosomally encoded Cu2+ P-type ATPases have recently been recognized in Enterococcus hirae and these are closely homologous to the bacterial cadmium efflux ATPase and the human copper-deficiency disease Menkes gene product. The Cd2+-efflux ATPase of gram-positive bacteria is a large P-type ATPase, homologous to the muscle Ca2+ ATPase and the Na+/K+ ATPases of animals. The arsenic-resistance system of gram-negative bacteria functions as an oxyanion efflux ATPase for arsenite and presumably antimonite. However, the structure of the arsenic ATPase is fundamentally different from that of P-type ATPases. The absence of the arsA gene (for the ATPase subunit) in gram-positive bacteria raises questions of energy-coupling for arsenite efflux. The ArsC protein product of the arsenic-resistance operons of bothgram-positive acid gram-negative bacteria is an intracellular enzyme that reduces arsenate [As(V)] to arsenite [As(III)], the substrate forthe transport pump. Newly studied cation efflux systems for Cd2+, Zn2, and Co2+ (CzC) or CO2+ and Ni2+ resistance (Cnr) lack ATPase motifsin their predicted polypeptide sequences. Therefore, not ail plasmid-resistance systems that function through toxic ion efflux are ATPases. The first well-defined bacterial metallothionein was found in the cyanobacterium Synechococcus. Bacterial metallothionein is encoded by thesmtA gene and contains 56 amino acids, including nine cysteine residues (fewer than animal metallothioneins). The synthesis of Synechococcus metallothionein is regulated by a repressor protein, the product of the adjacent but separately transcribed smtB gene. Regulation of metallothionein synthesis occurs at different levels: quickly by derepression of repressor activity, or over a longer time by deletion of the repressor gene at fixed positions and by amplification of the metallothionein DNA region leading to multiple copies of the gene.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/09/20 alle ore 00:39:30