Person: Martín González, Ana María
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First Name
Ana María
Last Name
Martín González
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Biológicas
Department
Genética, Fisiología y Microbiología
Area
Microbiología
Identifiers
6 results
Search Results
Now showing 1 - 6 of 6
Item Structural and Functional Diversity of Microbial Metallothionein Genes(Microbial Diversity in the Genomic Era, 2018) Gutiérrez Fernández, Juan Carlos; Francisco Martínez, Patricia de; Amaro Torres, Francisco; Díaz, Silvia; Martín González, Ana María; Das, Surajit; Dash, Hirak RanjanIn the present review, we discussed the concept of metallothionein (MT) and analyzed the structural and functional diversity of microbial MTs, grouping them into three main groups; bacteria, fungi, and protists. Structural diversity is analyzed based on the primary, secondary, and/or tertiary structure of the proteins. Their ability to bind different metals is also analyzed in each microbial group. An in silico and phylogenetic analysis of MT sequences from the main microbial groups has been carried out. The wide functional diversity of these proteins and the regulation of the MT gene expression are also discussed. The presence of several paralog genes in many microorganisms provides a coordinated and multiple response against different types of environmental stressors. Likewise, the main possible biotechnological applications of these proteins are explored, such as molecular tools to design biosensors for evaluating metal contamination and in metal bioremediation.Item Selenium cytotoxicity in Tetrahymena thermophila: New clues about its biological effects and cellular resistance mechanisms(Science of the Total Environment, 2019) Romero Sobrino, Iván; Francisco Martínez, Patricia de; Gutiérrez, Juan Carlos; Martín González, Ana MaríaSelenium is an essential micronutrient but at high concentrations can produce severe cytotoxicity and genomic damage. We have evaluated the cytotoxicity, ultrastructural and mitochondrial alterations of the two main selenium inorganic species; selenite and selenate, in the eukaryotic microorganism Tetrahymena thermophila. In this ciliate, selenite is more toxic than selenate. Their LC50 values were calculated as 27.65 μM for Se(IV) and 56.88 mM for Se(VI). Significant levels of peroxides/hydroperoxides are induced under low-moderate selenite or selenate concentrations. Se(VI) exposures induce an immediate mitochondrial membrane depolarization. Selenium treated cells show an intense vacuolization and some of them present numerous discrete and small electrondense particles, probably selenium deposits. Mitochondrial fusion, an intense swelling in peripheral mitochondria and mitophagy are detected in selenium treated cells, especially in those exposed to Se (IV). qRT-PCR analysis of diverse genes, encoding relevant antioxidant enzymes or other proteins, like metallothioneins, involved in an environmental general stress response, have shown that they may be crucial against Se(IV) and/or Se (VI) cytotoxicity.Item AP-1 (bZIP) Transcription Factors as Potential Regulators of Metallothionein Gene Expression in Tetrahymena thermophila(Frontiers in Genetics, 2018) Francisco Martínez, Patricia de; Amaro Torres, Francisco; Martín González, Ana María; Gutiérrez Fernández, Juan CarlosMetallothioneins (MT) are multi-stress proteins mainly involved in metal detoxification. MT gene expression is normally induced by a broad variety of stimulus and its gene expression regulation mainly occurs at a transcriptional level. Conserved motifs in the Tetrahymena thermophila MT promoters have been described. These motifs show a consensus sequence very similar to AP-1 sites, and bZIP type transcription factors might participate in the MT gene expression regulation. In this research work, we characterize four AP-1 transcription factors in each of four different analyzed Tetrahymena species, detecting a high conservation among them. Each AP-1 molecule has its counterpart in the other three Tetrahymena species. A comparative qRT-PCR analysis of these AP-1 genes have been carried out in different T. thermophila strains (including metal-adapted, knockout and/or knockdown strains among others), and under different metal-stress conditions (1 or 24 h Cd2+, Cu2+, or Pb2+ treatments). The possible interaction of these transcription factors with the conserved AP-1 motifs present in MT promoters has been corroborated by protein-DNA interaction experiments. Certain connection between the expression patterns of the bZIP and MT genes seems to exist. For the first time, and based on our findings, a possible gene expression regulation model including both AP-1 transcription factors and MT genes from the ciliate T. thermophila has been elaborated.Item Hints for Metal-Preference Protein Sequence Determinants: Different Metal Binding Features of the Five Tetrahymena thermophila Metallothioneins(International Journal of Biological Sciences, 2015) Espart, Anna; Marín, Maribel; Gil Moreno, Selene; Palacios, Óscar; Amaro Torres, Francisco; Martín González, Ana María; Gutiérrez Fernández, Juan Carlos; Capdevilla, Mercé; Atrian, SílviaThe metal binding preference of metallothioneins (MTs) groups them in two extreme subsets, the Zn/Cd- and the Cu-thioneins. Ciliates harbor the largest MT gene/protein family reported so far, in-cluding 5 paralogs that exhibit relatively low sequence similarity, excepting MTT2 and MTT4. In Tet-rahymena thermophila, three MTs (MTT1, MTT3 and MTT5) were considered Cd-thioneins and two (MTT2 and MTT4) Cu-thioneins, according to gene expression inducibility and phylogenetic analysis. In this study, the metal-binding abilities of the five MTT proteins were characterized, to obtain information about the folding and stability of their cognate- and non-cognate metal complexes, and to characterize the T. thermophila MT system at protein level. Hence, the five MTTs were recombinantly synthesized as Zn2+-, Cd2+- or Cu+-complexes, which were analyzed by electrospray mass spectrometry (ESI-MS), circular dichroism (CD), and UV-vis spectrophotometry. Among the Cd-thioneins, MTT1 and MTT5 were optimal for Cd2+ coordination, yielding unique Cd17- and Cd8- complexes, respectively. When binding Zn2+, they rendered a mixture of Zn-species. Only MTT5 was capable to coordinate Cu+, although yielding heteronuclear Zn-, Cu-species or highly unstable Cu-homometallic species. MTT3 exhibited poor binding abilities both for Cd2+ and for Cu+, and although not optimally, it yielded the best result when coordinating Zn2+. The two Cu-thioneins, MTT2 and MTT4 isoforms formed homometallic Cu-complexes (major Cu20-MTT) upon synthesis in Cu-supplemented hosts. Contrarily, they were unable to fold into stable Cd-complexes, while Zn-MTT species were only recovered for MTT4 (major Zn10-MTT4). Thus, the metal binding preferences of the five T. thermophila MTs correlate well with their previous classification as Cd- and Cu-thioneins, and globally, they can be classified from Zn/Cd- to Cu-thioneins according to the gradation: MTT1>MTT5>MTT3>MTT4>MTT2. The main mechanisms underlying the evolution and specialization of the MTT metal binding preferences may have been in-ternal tandem duplications, presence of doublet and triplet Cys patterns in Zn/Cd-thioneins, and op-timization of site specific amino acid determinants (Lys for Zn/Cd- and Asn for Cu-coordination).Item Heavy metal whole-cell biosensors using eukaryotic microorganisms: An updated critical review(Frontiers in Microbiology, 2015) Gutiérrez Fernández, Juan Carlos; Amaro Torres, Francisco; Martín González, Ana MaríaThis review analyzes the advantages and disadvantages of using eukaryotic microorganisms to design whole-cell biosensors (WCBs) for monitoring environmental heavy metal pollution in soil or aquatic habitats. Basic considerations for designing a eukaryotic WCB are also shown. A comparative analysis of the promoter genes used to design WCBs is carried out, and the sensitivity and reproducibility of the main reporter genes used is also reviewed. Three main eukaryotic taxonomic groups are considered: yeasts, microalgae, and ciliated protozoa. Models that have been widely analyzed as potential WCBs are the Saccharomyces cerevisiae model among yeasts, the Tetrahymena thermophila model for ciliates and Chlamydomonas model for microalgae. The advantages and disadvantages of each microbial group are discussed, and a ranking of sensitivity to the same type of metal pollutant from reported eukaryotic WCBs is also shown. General conclusions and possible future developments of eukaryotic WCBs are reported.Item Extreme metal adapted, knockout and knockdown strains reveal a coordinated gene expression among different Tetrahymena thermophila metallothionein isoforms(PLoS ONE, 2017) Francisco Martínez, Patricia de; Martín González, Ana María; Turkewitz, Aaron P.; Gutiérrez Fernández, Juan CarlosMetallothioneins (MT) constitute a superfamily of small cytosolic proteins that are able to bind metal cations through numerous cysteine (Cys) residues. Like other organisms the ciliate Tetrahymena thermophila presents several MT isoforms, which have been classified into two subfamilies (Cd- and Cu-metallothioneins). The main aim of this study was to examine the specific functions and transcriptional regulation of the five MT isoforms present in T. thermophila, by using several strains of this ciliate. After a laboratory evolution experiment over more than two years, three different T. thermophila strains adapted to extreme metal stress (Cd2+, Cu2+ or Pb2+) were obtained. In addition, three knockout and/or knockdown strains for different metallothionein (MT) genes were generated. These strains were then analyzed for expression of the individual MT isoforms. Our results provide a strong basis for assigning differential roles to the set of MT isoforms. MTT1 appears to have a key role in adaptation to Cd. In contrast, MTT2/4 are crucial for Cu-adaptation and MTT5 appears to be important for Pb-adaptation and might be considered as an “alarm” MT gene for responding to metal stress. Moreover, results indicate that likely a coordinated transcriptional regulation exists between the MT genes, particularly among MTT1, MTT5 and MTT2/4. MTT5 appears to be an essential gene, a first such report in any organism of an essential MT gene.