scholarly journals Identification and characterization of Pseudomonas membrane transporters necessary for utilization of the siderophore pyridine-2,6-bis(thiocarboxylic acid) (PDTC)

Microbiology ◽  
2006 ◽  
Vol 152 (10) ◽  
pp. 3157-3166 ◽  
Author(s):  
Lynne H. Leach ◽  
Thomas A. Lewis
Keyword(s):  
Outer Membrane ◽  
Transcriptional Activation ◽  
Iron Acquisition ◽  
Membrane Transporters ◽  
Membrane Transporter ◽  
Inner Membrane ◽  
Thiocarboxylic Acid ◽  
Outer Membrane Transporter ◽  
Identification And Characterization

The compound pyridine-2,6-bis(thiocarboxylic acid) (PDTC) is known to be produced and excreted by three strains of Pseudomonas. Its reactivity includes the complete dechlorination of the environmental contaminant carbon tetrachloride. PDTC functions as a siderophore; however, roles as a ferric reductant and antimicrobial agent have also been proposed. PDTC function and regulation were further explored by characterizing the phenotypes of mutants in predicted membrane transporter genes. The functions of a predicted outer-membrane transporter (PdtK) and a predicted inner-membrane permease (PdtE) were examined in Pseudomonas putida DSM 3601. Uptake of iron from 55Fe(III):PDTC, and bioutilization of PDTC in a chelated medium, were dependent upon PdtK and PdtE. Another strain of P. putida (KT2440), which lacks pdt orthologues, showed growth inhibition by PDTC that could be relieved by introducing a plasmid containing pdtKCPE. Transcriptional activation in response to exogenously added PDTC (25 μM) was unaltered by the pdtK or pdtE mutations; each mutant showed activation of a pdt transcriptional reporter, indistinguishable from an isogenic PDTC utilization-proficient strain. The data demonstrate that PdtK and PdtE constitute a bipartite outer-membrane/inner-membrane transport system for iron acquisition from Fe(III):PDTC. Disruptions in this portion of the P. putida DSM 3601 pdt gene cluster do not abolish PDTC-dependent transcriptional signalling.

scholarly journals Identification and Characterization of a Streptococcus pyogenes Operon Involved in Binding of Hemoproteins and Acquisition of Iron

2003 ◽  
Vol 71 (3) ◽  
pp. 1042-1055 ◽  
Author(s):  
Christopher S. Bates ◽  
Griselle E. Montañez ◽  
Charles R. Woods ◽  
Rebecca M. Vincent ◽  
Zehava Eichenbaum
Keyword(s):  
Hydrogen Peroxide ◽  
Streptococcus Pyogenes ◽  
Iron Acquisition ◽  
Iron Complex ◽  
Surface Proteins ◽  
Leader Peptide ◽  
Hemoglobin Binding ◽  
Membrane Bound ◽  
Identification And Characterization

ABSTRACT The hemolytic Streptococcus pyogenes can use a variety of heme compounds as an iron source. In this study, we investigate hemoprotein utilization by S. pyogenes. We demonstrate that surface proteins contribute to the binding of hemoproteins to S. pyogenes. We identify an ABC transporter from the iron complex family named sia for streptococcal iron acquisition, which consists of a lipoprotein (siaA), membrane permease (siaB), and ATPase (siaC). The sia transporter is part of a highly conserved, iron regulated, 10-gene operon. SiaA, which was localized to the cell membrane, could specifically bind hemoglobin. The operon's first gene encodes a novel bacterial protein that bound hemoglobin, myoglobin, heme-albumin, and hemoglobin-haptoglobin (but not apo-haptoglobin) and therefore was named Shr, for streptococcal hemoprotein receptor. PhoZ fusion and Western blot analysis showed that Shr has a leader peptide and is found in both membrane-bound and soluble forms. An M1 SF370 strain with a polar mutation in shr was more resistant to streptonigrin and hydrogen peroxide, suggesting decreased iron uptake. The addition of hemoglobin to the culture medium increased cell resistance to hydrogen peroxide in SF370 but not in the mutant, implying the sia operon may be involved in hemoglobin-dependent resistance to oxidative stress. The shr mutant demonstrated reduced hemoglobin binding, though cell growth in iron-depleted medium supplemented with hemoglobin, whole blood, or ferric citrate was not affected, suggesting additional systems are involved in hemoglobin utilization. SiaA and Shr are the first hemoprotein receptors identified in S. pyogenes; their possible role in iron capture is discussed.

scholarly journals Identification and characterization of Drosophila relatives of the yeast transcriptional activator SNF2/SWI2.

1994 ◽  
Vol 14 (4) ◽  
pp. 2225-2234 ◽  
Author(s):  
L K Elfring ◽  
R Deuring ◽  
C M McCallum ◽  
C L Peterson ◽  
J W Tamkun
Keyword(s):  
Transcriptional Activation ◽  
Slow Growth ◽  
Transcriptional Activator ◽  
Yeast Cells ◽  
Homeotic Genes ◽  
Dependent Atpase ◽  
Functional Homolog ◽  
Identification And Characterization

The Drosophila brahma (brm) gene encodes an activator of homeotic genes that is highly related to the yeast transcriptional activator SWI2 (SNF2), a potential helicase. To determine whether brm is a functional homolog of SWI2 or merely a member of a family of SWI2-related genes, we searched for additional Drosophila genes related to SWI2 and examined their function in yeast cells. In addition to brm, we identified one other Drosophila relative of SWI2: the closely related ISWI gene. The 1,027-residue ISWI protein contains the DNA-dependent ATPase domain characteristic of the SWI2 protein family but lacks the three other domains common to brm and SWI2. In contrast, the ISWI protein is highly related (70% identical) to the human hSNF2L protein over its entire length, suggesting that they may be functional homologs. The DNA-dependent ATPase domains of brm and SWI2, but not ISWI, are functionally interchangeable; a chimeric SWI2-brm protein partially rescued the slow growth of swi2- cells and supported transcriptional activation mediated by the glucocorticoid receptor in vivo in yeast cells. These findings indicate that brm is the closest Drosophila relative of SWI2 and suggest that brm and SWI2 play similar roles in transcriptional activation.

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