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Lunavat SK, Singh SS, Mohammed AQ, Nakka VP, Phanithi PB, Medisetty R, Gogada R. The MreA Metal-Binding Sites C40, H65, and C69 Play a Critical Role in the Metal Tolerance of Pseudomonas putida KT2440. Curr Microbiol 2022; 79:142. [PMID: 35322302 DOI: 10.1007/s00284-022-02804-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Metal-binding proteins occur in the cytosol of most eubacteria. The hypothetical metal responsive protein MreA (PP-2969 gene; NreA) seems responsible for zinc, chromium, cadmium accumulation, and metal ion homeostasis. However, there is a lack of definitive evidence regarding the specific metal-binding sites of MreA protein. The present study aimed to identify putative metal-binding regions for MreA. In silico analysis revealed that amino acids C40, H65, and C69 (CHC region) seem critical for metal-protein interactions. We created site-directed mutants (SDM's) of MreA for interacted amino acids to validate in silico results. The differential scanning fluorimetry (DSF) and atomic absorption spectroscopy (AAS) showed that SDM strains of MreA protein curtailed metal accumulation compared to the wild types indicating C40, H65, and C69 amino acids are critical for metal binding. Thus, we report potential implications for MreA-bioengineered strains of Pseudomonas putida KT2440 for metal ion homeostasis by alleviating metal toxicity in the biological environment.
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Affiliation(s)
- Shanti Kumari Lunavat
- Department of Biochemistry, Osmania University, Hyderabad, Telangana, 500 007, India
| | | | - Abdul Qadeer Mohammed
- Department of Biochemistry, Osmania University, Hyderabad, Telangana, 500 007, India
| | - Venkata Prasuja Nakka
- Department of Biochemistry, Acharya Nagarjuna University, Guntur, Andhra Pradesh, 522510, India
| | - Prakash-Babu Phanithi
- Department of Biotechnology and Bioinformatics, University of Hyderabad, Hyderabad, Telangana, 500046, India
| | - Rajesh Medisetty
- Department of Biochemistry, Osmania University, Hyderabad, Telangana, 500 007, India
| | - Raghu Gogada
- Department of Biotechnology and Bioinformatics, University of Hyderabad, Hyderabad, Telangana, 500046, India.
- Department of Biochemistry, Osmania University, Hyderabad, Telangana, 500 007, India.
- Department of Biochemistry and Plant Physiology, MS Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakhemundi, Odisha, 761211, India.
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Affiliation(s)
- N. Singh
- Department of Botany, Fourah Bay College, University of Sierra Leone, Freetown, Sierra Leone
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Korripally P, Tiwari A, Haritha A, Kiranmayi P, Bhanoori M. Characterization of Ctr family genes and the elucidation of their role in the life cycle of Neurospora crassa. Fungal Genet Biol 2009; 47:237-45. [PMID: 20034585 DOI: 10.1016/j.fgb.2009.12.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2009] [Revised: 12/07/2009] [Accepted: 12/15/2009] [Indexed: 10/20/2022]
Abstract
Transcriptional analysis using qRT-PCR of 62 metal ion transporters during conidial germination of Neurospora crassa showed a significant up regulation of a hypothetical copper transporter gene, tcu-1, that belongs to the Ctr family. Herein we characterised the Ctr family genes (tcu-1, tcu-2 and tcu-3) and deciphered their role in various developmental phases of the N. crassa life cycle. Cross complementation assays in copper uptake mutant of Saccharomyces cerevisiae revealed that tcu-1, tcu-2 and tcu-3 are functional homologs of S. cerevisiae copper transporters. Expression studies of Ctr family members in various developmental phases of N. crassa showed differential expression pattern for high-affinity copper transporter, TCU1. Functional analysis of their gene knockout mutants showed that tcu-1 is essential for saprophytic conidial germination, vegetative growth and perithecia development under copper limited conditions while conidiation remained unaffected.
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Affiliation(s)
- Premsagar Korripally
- Department of Biochemistry, University College of Science, Osmania University, Hyderabad 500 007, India
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MrdH, a novel metal resistance determinant of Pseudomonas putida KT2440, is flanked by metal-inducible mobile genetic elements. J Bacteriol 2009; 191:5976-87. [PMID: 19648243 DOI: 10.1128/jb.00465-09] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We report here the identification and characterization of mrdH, a novel chromosomal metal resistance determinant, located in the genomic island 55 of Pseudomonas putida KT2440. It encodes for MrdH, a predicted protein of approximately 40 kDa with a chimeric domain organization derived from the RcnA and RND (for resistance-nodulation-cell division) metal efflux proteins. The metal resistance function of mrdH was identified by the ability to confer nickel resistance upon its complementation into rcnA mutant (a nickel- and cobalt-sensitive mutant) of Escherichia coli. However, the disruption of mrdH in P. putida resulted in an increased sensitivity to cadmium and zinc apart from nickel. Expression studies using quantitative reverse transcription-PCR showed the induction of mrdH by cadmium, nickel, zinc, and cobalt. In association with mrdH, we also identified a conserved hypothetical gene mreA whose encoded protein showed significant homology to NreA and NreA-like proteins. Expression of the mreA gene in rcnA mutant of E. coli enhanced its cadmium and nickel resistance. Transcriptional studies showed that both mrdH and mreA underwent parallel changes in gene expression. The mobile genetic elements Tn4652 and IS1246, flanking mrdH and mreA were found to be induced by cadmium, nickel, and zinc, but not by cobalt. This study is the first report of a single-component metal efflux transporter, mrdH, showing chimeric domain organization, a broad substrate spectrum, and a location amid metal-inducible mobile genetic elements.
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Sowjanya TN, Mohan PM. A calcium binding protein from cell wall of Neurospora crassa. J Basic Microbiol 2009; 49:371-6. [PMID: 19322841 DOI: 10.1002/jobm.200800304] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Isolated cell wall preparations of N. crassa bind significant levels of Ca, Mg and other divalent cations. Enzymatic treatment of the cell wall with beta-(1,3)-glucanase, but not with chitinase, resulted in solubilization of only the calcium-binding protein fraction. A calcium-binding protein (CaBP) was purified by metal-chelate affinity chromatography and reversed phase HPLC. CaBP has an Mr of around 6 kDa on SDS-PAGE and mass spectrometry showed that it has a molecular mass of 5744 Da. One mole of CaBP binds 2 moles of calcium and is partially inhibited (15-50%) by other divalent cations (Mg, Ni and Cu). Quenching of tryptophan fluorescence was observed upon copper binding but not calcium binding. This is a first report of a calcium binding protein from the cell wall of fungi.
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Functional characterization of tzn1 and tzn2-zinc transporter genes in Neurospora crassa. Biometals 2008; 22:411-20. [PMID: 18989627 DOI: 10.1007/s10534-008-9177-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2008] [Accepted: 10/24/2008] [Indexed: 10/21/2022]
Abstract
Previous work from our laboratory involved the description of the Neurospora metal transportome, which included seven hypothetical zinc transporters belonging to the ZIP family. The aim of the present study was to make a comparative functional evaluation of two hypothetical zinc transporters named tzn1 (NCU07621.3) and tzn2 (NCU11414.3). Phenotypic analysis of tzn1 and tzn2 mutants and a double mutant (tzn1tzn2) revealed that the deletion of tzn1 causes aconidiation and a greater defect in growth than the single deletion of tzn2. Supplementation with zinc restores growth but not conidiation in tzn1 and tzn1tzn2. TZN1 complemented a zinc-uptake-deficient Saccharomyces cerevisiae mutant (zrt1zrt2) in zinc-deficient conditions, while tzn2 restored growth upon supplementation with zinc (0.05 mM). Furthermore, the Deltatzn1 mutant was found to have severely reduced zinc content indicating that tzn1 functions as a key regulator of intracellular zinc levels in Neurospora crassa. Zinc uptake studies indicate tzn1 is a specific transporter of zinc, while tzn2 transports both zinc and cadmium. Quantitative RT-PCR showed up-regulation of tzn1 (128-fold) under zinc-depleted conditions and down-regulation (>1,000-fold) in zinc-replete conditions. The present study indicates that the zinc transport proteins encoded by tzn1 and tzn2 are members of the zinc uptake system regulated by zinc status in N. crassa.
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Tripathi P, Srivastava S. Mechanism to combat cobalt toxicity in cobalt resistant mutants of Aspergillus nidulans. Indian J Microbiol 2007; 47:336-44. [PMID: 23100687 DOI: 10.1007/s12088-007-0061-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2007] [Accepted: 11/02/2007] [Indexed: 11/30/2022] Open
Abstract
Characteristics of fungal species tolerant to high levels of metals in natural environment can be amplified by isolation and selection of resistant mutants. Step-by-step culturing led to identification of highly stable Co-resistant (Co(R)) mutants of A. nidulans. Based on two distinct morphological features, Co-resistant mutants were categorized as Co(R)I and Co(R)II. The two mutants varied in their growth behavior and colony morphology that were reflected in supplemented as well as unsupplemented growth media over the generations. As compared to the Co(R)I, Co(R)II mutant exhibited sparse mycelia and conidiation but secreted higher amount of melanin. Co(R) mutants could tolerate up to 2.5mM Co in the medium, however, required a threshold concentration of 0.25mM Co for optimal growth and germination. Absence of Co in the medium caused a stressful situation for the Co(R) mutants and led to the secretion of a white extracellular precipitate found to be a glycoprotein. In response to interactions with Co-ions, Co(R) mutants produced oxalic acid and bioprecipitated Co as Co-oxalate providing scope for metal reclamation as well as oxalic acid extraction. The mutants could help to recover the insoluble Co-oxalate salt from aqueous solutions by entrapping it in their growing mycelial meshwork.
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Affiliation(s)
- Pushplata Tripathi
- School of sciences, Indira Gandhi National Open University, New Delhi, 110 068 India
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Karna RR, Sajani LS, Mohan PM. Bioaccumulation and biosorption of Co2+ by Neurospora crassa. Biotechnol Lett 1996. [DOI: 10.1007/bf00128593] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Use of wild type and nickel resistantNeurospora crassa for removal of Ni2+ from aqueous medium. Biotechnol Lett 1992. [DOI: 10.1007/bf01021067] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Venkateswerlu G, Stotzky G. Binding of metals by cell walls of Cunninghamella blakesleeana grown in the presence of copper or cobalt. Appl Microbiol Biotechnol 1989. [DOI: 10.1007/bf00270806] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Excretion of pyruvate in nickel toxicity in wild type and Ni2+ resistant mutants ofNeurospora crassa. J Biosci 1984. [DOI: 10.1007/bf02716742] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Mohan PM, Sastry KS. Cobalt transport in nickel-resistant strains ofNeurospora crassa. Curr Microbiol 1984. [DOI: 10.1007/bf01567338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Mohan PM, Sastry KS. Studies on copper toxicity in nickel-resistant strains ofNeurospora crassa. Curr Microbiol 1983. [DOI: 10.1007/bf01567284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Maruthi Mohan P, Sivarama Sastry K. Interrelationships in trace-element metabolism in metal toxicities in nickel-resistant strains of Neurospora crassa. Biochem J 1983; 212:205-10. [PMID: 6223632 PMCID: PMC1152030 DOI: 10.1042/bj2120205] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Three different Ni2+-resistant strains of Neurospora crassa (NiR1, NiR2 and NiR3) have been isolated. All are stable mutants and are fourfold more resistant to Ni2+ than the parent wild-type strain. NiR1 and NiR2 are also sixfold more resistant to Co2+, whereas NiR3 is only twice as resistant to Co2+; the former two are also twofold more resistant to Zn2+, but NiR3 is not. These three strains also differ in sensitivity to Cu2+. Toxicities and concomitant accumulation patterns of Ni2+, Co2+ and Cu2+ have been examined in these strains. NiR1 and NiR2, despite quantitative individual differences, generally accumulate very high amounts of Ni2+ and Co2+, and Mg2+ reverses the toxicities of these two ions by different mechanisms; Ni2+ uptake is suppressed, but not that of Co2+. In NiR3, Mg2+ controls uptake of both Ni2+ and Co2+. Studies indicate that two kinds of Ni2+-resistant strains of N. crassa exist; one kind is resistant because it can tolerate high intracellular concentrations of heavy-metal ions, whereas the other is resistant because it can control metal-ion accumulation.
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Venkateswerlu G, Sivarama Sastry K. A new repressible alkaline phosphatase inNeurospora crassa EM 5297a. J Biosci 1982. [DOI: 10.1007/bf02702739] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Nirmala J, Sivarama Sastry K. The effect of thiourea on ureide metabolism in Neurospora crassa. Biochem J 1973; 136:749-55. [PMID: 4273557 PMCID: PMC1166011 DOI: 10.1042/bj1360749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The wild-type strain of Neurospora crassa Em 5297a can utilize allantoin as a sole nitrogen source. The pathway of allantoin utilization is via its conversion into allantoic acid and urea, followed by the breakdown of urea to ammonia. This is shown by the inability of the urease-less mutant, N. crassa 1229, to grow on allantoin as a sole nitrogen source and by the formation of allantoate and urea by pre-formed mycelia of this mutant. In the wild strain (Em 5297a) thiourea is tenfold more toxic on an allantoin medium than on an inorganic nitrogen medium; allantoin as well as urea counteract thiourea toxicity in the allantoin nitrogen medium. This selective toxicity of thiourea for the mould utilizing allantoin nitrogen does not, however, result in an impairment of allantoin uptake, allantoinase activity or the formation of urea from allantoin. The only process affected by thiourea is the synthesis of urease; urea antagonizes this effect of thiourea in N. crassa.
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