The Structure and Function of Catalytic Domains Within Inositol Polyphosphate 5‐Phosphatases

Whisstock, James C.; Wiradjaja, Fenny; Waters, Joanne; Gurung, Rajendra

doi:10.1080/15216540210814

Cited by 47 publications

(47 citation statements)

References 81 publications

(89 reference statements)

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“…It was proposed that the 5PTases share a common mechanism for catalysis with a family of Mg 2þ -dependent nucleases, including DNase I and the apurinic/apyrimidinic base excision repair endonucleases (Whisstock et al, 2002). Because FRA3 shows high sequence similarity to 5PTases from yeast and animals, it was not surprising to find that FRA3 also requires Mg 2þ for its activity.…”

Section: Fra3 Contains a Wd-repeat Domainmentioning

confidence: 99%

“…In addition to the phosphatase catalytic domain, some type II 5PTases in yeast and animals possess additional modules, such as SAC domain, Rho GTPase activating protein domain, and Pro-rich domain (Whisstock et al, 2002). The SAC domain in synaptojanins has been shown to hydrolyze 3-or 4-position phosphate from PtdIns(3)P, PtdIns(4)P, or PtdIns(3,5)P 2 , and together with the activity of the type II 5PTase domain, it has been thought to be able to completely terminate the phosphoinositide signaling molecules (Hughes et al, 2000).…”

Section: Fra3 Contains a Wd-repeat Domainmentioning

confidence: 99%

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FRAGILE FIBER3, an Arabidopsis Gene Encoding a Type II Inositol Polyphosphate 5-Phosphatase, Is Required for Secondary Wall Synthesis and Actin Organization in Fiber Cells

et al. 2004

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Type II inositol polyphosphate 5-phosphatases (5PTases) in yeast and animals have been known to regulate the level of phosphoinositides and thereby influence various cellular activities, such as vesicle trafficking and actin organization. In plants, little is known about the phosphatases involved in hydrolysis of phosphoinositides, and roles of type II 5PTases in plant cellular functions have not yet been characterized. In this study, we demonstrate that the FRAGILE FIBER3 (FRA3) gene of Arabidopsis thaliana, which encodes a type II 5PTase, plays an essential role in the secondary wall synthesis in fiber cells and xylem vessels. The fra3 mutations caused a dramatic reduction in secondary wall thickness and a concomitant decrease in stem strength. These phenotypes were associated with an alteration in actin organization in fiber cells. Consistent with the defective fiber and vessel phenotypes, the FRA3 gene was found to be highly expressed in fiber cells and vascular tissues in stems. The FRA3 protein is composed of two domains, an N-terminal localized WD-repeat domain and a C-terminal localized 5PTase catalytic domain. In vitro activity assay demonstrated that recombinant FRA3 exhibited phosphatase activity toward PtdIns(4,5)P 2 , PtdIns(3,4,5)P 3 , and Ins(1,4,5)P 3 , with the highest substrate affinity toward PtdIns(4,5)P 2 . The fra3 missense mutation, which caused an amino acid substitution in the conserved motif II of the 5PTase catalytic domain, completely abolished the FRA3 phosphatase activity. Moreover, the endogenous levels of PtdIns(4,5) 2 and Ins(1,4,5)P 3 were found to be elevated in fra3 stems. Together, our findings suggest that the FRA3 type II 5PTase is involved in phosphoinositide metabolism and influences secondary wall synthesis and actin organization.

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Section: Fra3 Contains a Wd-repeat Domainmentioning

confidence: 99%

Section: Fra3 Contains a Wd-repeat Domainmentioning

confidence: 99%

FRAGILE FIBER3, an Arabidopsis Gene Encoding a Type II Inositol Polyphosphate 5-Phosphatase, Is Required for Secondary Wall Synthesis and Actin Organization in Fiber Cells

et al. 2004

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“…In plants, no homologs of bifunctional synaptojanin-like enzymes have been identified. Although we cannot find any sequences within SAC9 that suggest it is a plant homolog of a synaptojanin, we do note that its in vivo function more closely resembles that of a synaptojanin than other SAC domain proteins (Mitchell et al, 2002;Whisstock et al, 2002). In vitro expression and activity studies of full-length and truncated SAC9 proteins will determine if a cryptic catalytic activity can be detected in the C-terminal domain.…”

Section: Specificity and Structure Of Pi Phosphatasesmentioning

confidence: 99%

“…PtdIns(4,5)P 2 signaling is terminated through the action of two types of phosphatases. The type II inositol polyphosphate 5-phosphatases (5PTases) act on both PIs and soluble inositol phosphates, while the Sac domain phosphatases are thought to act only on PIs (Mitchell et al, 2002;Whisstock et al, 2002).…”

mentioning

confidence: 99%

Mutations in the Arabidopsis Phosphoinositide Phosphatase Gene SAC9 Lead to Overaccumulation of PtdIns(4,5)P2 and Constitutive Expression of the Stress-Response Pathway

et al. 2005

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Phosphoinositides (PIs) are signaling molecules that regulate cellular events including vesicle targeting and interactions between membrane and cytoskeleton. Phosphatidylinositol (PtdIns)(4,5)P 2 is one of the best characterized PIs; studies in which PtdIns(4,5)P 2 localization or concentration is altered lead to defects in the actin cytoskeleton and exocytosis. PtdIns(4,5)P 2 and its derivative Ins(1,4,5)P 3 accumulate in salt, cold, and osmotically stressed plants. PtdIns(4,5)P 2 signaling is terminated through the action of inositol polyphosphate phosphatases and PI phosphatases including supressor of actin mutation (SAC) domain phosphatases. In some cases, these phosphatases also act on Ins(1,4,5)P 3 . We have characterized the Arabidopsis (Arabidopsis thaliana) sac9 mutants. The SAC9 protein is different from other SAC domain proteins in several ways including the presence of a WW protein interaction domain within the SAC domain. The rice (Oryza sativa) and Arabidopsis SAC9 protein sequences are similar, but no apparent homologs are found in nonplant genomes. High-performance liquid chromatography studies show that unstressed sac9 mutants accumulate elevated levels of PtdIns(4,5)P 2 and Ins(1,4,5)P 3 as compared to wildtype plants. The sac9 mutants have characteristics of a constitutive stress response, including dwarfism, closed stomata, and anthocyanin accumulation, and they overexpress stress-induced genes and overaccumulate reactive-oxygen species. These results suggest that the SAC9 phosphatase is involved in modulating phosphoinsitide signals during the stress response.Phosphoinositides (PIs) are a family of eight molecules in which the hydroxyl groups on the inositol moiety can be phosphorylated in a variety of combinations (Stevenson et al., 2000;Meijer and Munnik, 2003;van Leeuwen et al., 2004). PIs undergo cycles of phosphorylation and dephosphorylation through organelle-specific PI kinases and phosphatases, leading to distinct subcellular distributions of PI species (De Matteis and Godi, 2004). PIs control the timing and location of many cellular events including vesicle targeting, interactions between the membrane and the cytoskeleton, membrane budding and fusing, nuclear and cytoplasmic signal transduction, and activity of membrane channels (Hilgemann and Ball, 1996;Martin, 1998;Czech, 2000;Odorizzi et al., 2000;Stevenson et al., 2000; Simonsen et al., 2001;Hardie, 2003;Meijer and Munnik, 2003;Oliver et al., 2004;van Leeuwen et al., 2004). Specific PI-binding sites have been found on a variety of effector proteins including protein kinases, actin-binding proteins, GTPases, and membrane trafficking proteins, and it is thought that binding to PIs can target effector proteins to specific membrane locations (Martin, 1998;Hu et al., 1999;Yao et al., 1999;Dowler et al., 2000;Tall et al., 2000;Ellson et al., 2002;Itoh and Takenawa, 2002).Unraveling the specific functions of the PI species and the enzymes that modify them is challenging for several reasons. Enzyme specificities do not always correlate ...

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“…The residues at positions 84 (N), 119 (E), 169 (E), 238 (H), 289 (D), 291 (N), 336 (D), 398 (D), and 399 (H) in MBOVPG45_0215 (Table 3) are highly conserved and comprise the active catalytic site (34). Residues 84, 119, 289, 336, 398, and 399 can be predicted to be involved in the binding of magnesium ions (34), and those at positions 86 (L), 238, 289, 291, and 399 can be predicted to comprise a putative phosphate binding site (35).…”

Section: Identification Of Disruptions In Nuclease Genesmentioning

confidence: 99%

Disruption of the Membrane Nuclease Gene (MBOVPG45_0215) of Mycoplasma bovis Greatly Reduces Cellular Nuclease Activity

et al. 2015

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Although the complete genome sequences of three strains of Mycoplasma bovis are available, few studies have examined gene function in this important pathogen. Mycoplasmas lack the biosynthetic machinery for the de novo synthesis of nucleic acid precursors, so nucleases are likely to be essential for them to acquire nucleotide precursors. Three putative membrane nucleases have been annotated in the genome of M. bovis strain PG45, MBOVPG45_0089 and MBOVPG45_0310, both of which have the thermonuclease (TNASE_3) functional domain, and MBOVPG45_0215 (mnuA), which has an exonuclease/endonuclease/phosphatase domain. While previous studies have demonstrated the function of TNASE_3 domain nucleases in several mycoplasmas, quantitative comparisons of the contributions of different nucleases to cellular nuclease activity have been lacking. Mapping of a library of 319 transposon mutants of M. bovis PG45 by direct genome sequencing identified mutants with insertions in MBOVPG45_0310 (the ⌬0310 mutant) and MBOVPG45_0215 (the ⌬0215 mutant). In this study, the detection of the product of MBOVPG45_0215 in the Triton X-114 fraction of M. bovis cell lysates, its cell surface exposure, and its predicted signal peptide suggested that it is a surface-exposed lipoprotein nuclease. Comparison of a ⌬mnuA mutant with wild-type M. bovis on native and denatured DNA gels and in digestion assays using double-stranded phage DNA and closed circular plasmid DNA demonstrated that inactivation of this gene abolishes most of the cellular exonuclease and endonuclease activity of M. bovis. This activity could be fully restored by complementation with the wild-type mnuA gene, demonstrating that MnuA is the major cellular nuclease of M. bovis. IMPORTANCENucleases are thought to be important contributors to virulence and crucial for the maintenance of a nutritional supply of nucleotides in mycoplasmas that are pathogenic in animals. This study demonstrates for the first time that of the three annotated cell surface nuclease genes in an important pathogenic mycoplasma, the homologue of the thermostable nuclease identified in Gram-positive bacteria is responsible for the majority of the nuclease activity detectable in vitro.A lthough the complete genomes of many Mycoplasma species are now available, the scarcity of tools for exploring their molecular biology has resulted in an understanding of the function of their genes more rudimentary than that which is available for many other prokaryotes. The genomes of three strains of the important bovine pathogen Mycoplasma bovis, the type strain PG45, the Hubei-1 strain, and the HB0801 strain, have been sequenced and published recently (1-3), but apart from several reports on phase switching in M. bovis (4-7), few studies have examined the molecular mechanisms underlying their pathogenicity and virulence or the metabolic functions of the products of their genes.Mycoplasmas evolved from Clostridium-like bacteria by a process of reductive evolution and are believed to have retained only the regulatory and ...

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The Structure and Function of Catalytic Domains Within Inositol Polyphosphate 5‐Phosphatases

Cited by 47 publications

References 81 publications

FRAGILE FIBER3, an Arabidopsis Gene Encoding a Type II Inositol Polyphosphate 5-Phosphatase, Is Required for Secondary Wall Synthesis and Actin Organization in Fiber Cells

FRAGILE FIBER3, an Arabidopsis Gene Encoding a Type II Inositol Polyphosphate 5-Phosphatase, Is Required for Secondary Wall Synthesis and Actin Organization in Fiber Cells

Mutations in the Arabidopsis Phosphoinositide Phosphatase Gene SAC9 Lead to Overaccumulation of PtdIns(4,5)P2 and Constitutive Expression of the Stress-Response Pathway

Disruption of the Membrane Nuclease Gene (MBOVPG45_0215) of Mycoplasma bovis Greatly Reduces Cellular Nuclease Activity

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