Artículos (Instituto de Bioquímica Vegetal y Fotosíntesis IBVF – CIC Cartuja)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10949

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Inorganic Polyphosphate in the Microbial World. Emerging Roles for a Multifaceted Biopolymer
(Springer Verlag, 2016) Albi Rodríguez, Tomás; Serrano Delgado, Aurelio; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Economía y Competitividad (MINECO). España; Junta de Andalucía
inorganic polyphosphates (polyP) are linear polymers of tens to hundreds orthophosphate residues linked by phosphoanhydride bonds. These fairly abundant biopolymers occur in all extant forms of life, from prokaryotes to mammals, and could have played a relevant role in prebiotic evolution. Since the first identification of polyP deposits as metachromatic or volutin granules in yeasts in the nineteenth century, an increasing number of varied physiological functions have been reported. Due to their "high energy" bonds analogous to those in ATP and their properties as polyanions, polyP serve as microbial phosphagens for a variety of biochemical reactions, as a buffer against alkalis, as a storage of Ca(2+) and as a metal-chelating agent. In addition, recent studies have revealed polyP importance in signaling and regulatory processes, cell viability and proliferation, pathogen virulence, as a structural component and chemical chaperone, and as modulator of microbial stress response. This review summarizes the current status of knowledge and future perspectives of polyP functions and their related enzymes in the microbial world.
Photoperiodic control of carbon distribution during the floral transition in Arabidopsis
(American Society of Plant Biologists, 2014) Ortíz Marchena, M Isabel; Albi Rodríguez, Tomás; Lucas Reina, Eva; Said, Fátima E.; Romero Campero, Francisco José; Cano Ruiz, Beatriz; Ruiz, M. Teresa; Romero Rodríguez, José María; Valverde Albacete, Federico; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Economía y Competitividad (MINECO). España; Junta de Andalucía
Flowering is a crucial process that demands substantial resources. Carbon metabolism must be coordinated with development through a control mechanism that optimizes fitness for any physiological need and growth stage of the plant. However, how sugar allocation is controlled during the floral transition is unknown. Recently, the role of a CONSTANS (CO) ortholog (Cr-CO) in the control of the photoperiod response in the green alga Chlamydomonas reinhardtii and its influence on starch metabolism was demonstrated. In this work, we show that transitory starch accumulation and glycan composition during the floral transition in Arabidopsis thaliana are regulated by photoperiod. Employing a multidisciplinary approach, we demonstrate a role for CO in regulating the level and timing of expression of the GRANULE BOUND STARCH SYNTHASE (GBSS) gene. Furthermore, we provide a detailed characterization of a GBSS mutant involved in transitory starch synthesis and analyze its flowering time phenotype in relation to its altered capacity to synthesize amylose and to modify the plant free sugar content. Photoperiod modification of starch homeostasis by CO may be crucial for increasing the sugar mobilization demanded by the floral transition. This finding contributes to our understanding of the flowering process
Two exopolyphosphatases with distinct molecular architectures and substrate specificities from the thermophilic green-sulfur bacterium Chlorobium tepidum TLS
(Microbiology Society, 2014) Albi Rodríguez, Tomás; Serrano Delgado, Aurelio; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Gobierno de España; Junta de Andalucía
The genome of the thermophilic green-sulfur bacterium Chlorobium tepidumTLS possesses two genes encoding putative exopolyphosphatases (PPX; EC 3.6.1.11), namely CT0099 (ppx1, 993 bp) and CT1713 (ppx2, 1557 bp). The predicted polypeptides of 330 and 518 aa residues are Ppx-GppA phosphatases of different domain architectures - the largest one has an extra C-terminal HD domain - which may represent ancient paralogues. Both ppxgenes were cloned and overexpressed in Escherichia coli BL21(DE3). While CtPPX1 was validated as a monomeric enzyme, CtPPX2 was found to be a homodimer. Both PPX homologues were functional, K+-stimulated phosphohydrolases, with an absolute requirement for divalent metal cations and a marked preference for Mg2+. Nevertheless, they exhibited remarkably different catalytic specificities with regard to substrate classes and chain lengths. Even though both enzymes were able to hydrolyse the medium-size polyphosphate (polyP) P13-18 (polyP mix with mean chain length of 13-18 phosphate residues), CtPPX1 clearly reached its highest catalytic efficiency with tripolyphosphate and showed substantial nucleoside triphosphatase (NTPase) activity, while CtPPX2 preferred long-chain polyPs (>300 Pi residues) and did not show any detectable NTPase activity. These catalytic features, taken together with the distinct domain architectures and molecular phylogenies, indicate that the two PPX homologues of Chl. tepidum belong to different Ppx-GppA phosphatase subfamilies that should play specific biochemical roles in nucleotide and polyP metabolisms. In addition, these results provide an example of the remarkable functional plasticity of the Ppx-GppA phosphatases, a family of proteins with relatively simple structures that are widely distributed in the microbial world. © 2014 The Authors.
Two strictly polyphosphate-dependent gluco(manno)kinases from diazotrophic Cyanobacteria with potential to phosphorylate hexoses from polyphosphates
(Springer, 2015) Albi Rodríguez, Tomás; Serrano, Aurelio
The single-copy genes encoding putative polyphosphate–glucose phosphotransferases (PPGK, EC 2.7.1.63) from two nitrogen-fixing Cyanobacteria, Nostoc sp. PCC7120 and Nostoc punctiforme PCC73102, were cloned and functionally characterized. In contrast to their actinobacterial counterparts, the cyanobacterial PPGKs have shown the ability to phosphorylate glucose using strictly inorganic polyphosphates (polyP) as phosphoryl donors. This has proven to be an economically attractive reagent in contrast to the more costly ATP. Cyanobacterial PPGKs had a higher affinity for medium–long-sized polyP (greater than ten phosphoryl residues). Thus, longer polyP resulted in higher catalytic efficiency. Also in contrast to most their homologs in Actinobacteria, both cyanobacterial PPGKs exhibited a modest but significant polyP-mannokinase activity as well. Specific activities were in the range of 180–230 and 2– 3 μmol min−1 mg−1 with glucose and mannose as substrates, respectively. No polyP-fructokinase activity was detected. Cyanobacterial PPGKs required a divalent metal cofactor and exhibited alkaline pH optima (approx. 9.0) and a remarkable thermostability (optimum temperature, 45 °C). The preference for Mg2+ was noted with an affinity constant of 1.3 mM. Both recombinant PPGKs are homodimers with a subunit molecular mass of ca. 27 kDa. Based on database searches and experimental data from Southern blots and activity assays, closely related PPGK homologs appear to be widespread among unicellular and filamentous mostly nitrogen-fixing Cyanobacteria. Overall, these findings indicate that polyP may be metabolized in these photosynthetic prokaryotes to yield glucose (or mannose) 6-phosphate. They also provide evidence for a novel group-specific subfamily of strictly polyP-dependent gluco(manno)kinases with ancestral features and high biotechnological potential, capable of efficiently using polyP as an alternative and cheap source of energy-rich phosphate instead of costly ATP. Finally, these results could shed new light on the evolutionary origin of sugar kinases

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Examinando Artículos (Instituto de Bioquímica Vegetal y Fotosíntesis IBVF – CIC Cartuja) por Autor "Albi Rodríguez, Tomás"