共查询到20条相似文献,搜索用时 78 毫秒
1.
2.
3.
Sandra Wydau Guillaume van der Rest Caroline Aubard Pierre Plateau Sylvain Blanquet 《The Journal of biological chemistry》2009,284(21):14096-14104
Several l-aminoacyl-tRNA synthetases can transfer a
d-amino acid onto their cognate tRNA(s). This harmful reaction is
counteracted by the enzyme d-aminoacyl-tRNA deacylase. Two distinct
deacylases were already identified in bacteria (DTD1) and in archaea (DTD2),
respectively. Evidence was given that DTD1 homologs also exist in nearly all
eukaryotes, whereas DTD2 homologs occur in plants. On the other hand, several
bacteria, including most cyanobacteria, lack genes encoding a DTD1 homolog.
Here we show that Synechocystis sp. PCC6803 produces a third type of
deacylase (DTD3). Inactivation of the corresponding gene (dtd3)
renders the growth of Synechocystis sp. hypersensitive to the
presence of d-tyrosine. Based on the available genomes, DTD3-like
proteins are predicted to occur in all cyanobacteria. Moreover, one or several
dtd3-like genes can be recognized in all cellular types, arguing in
favor of the nearubiquity of an enzymatic function involved in the defense of
translational systems against invasion by d-amino acids.Although they are detected in various living organisms (reviewed in Ref.
1), d-amino acids
are thought not to be incorporated into proteins, because of the
stereospecificity of aminoacyl-tRNA synthetases and of the translational
machinery, including EF-Tu and the ribosome
(2). However, the
discrimination between l- and d-amino acids by
aminoacyl-tRNA synthetases is not equal to 100%. Significant
d-aminoacylation of their cognate tRNAs by Escherichia
coli tyrosyl-, tryptophanyl-, aspartyl-, lysyl-, and histidyl-tRNA
synthetases has been characterized in vitro
(3–9).
Recently, using a bacterium, transfer of d-tyrosine onto
tRNATyr was shown to occur in vivo
(10).With such misacylation reactions, the resulting
d-aminoacyl-tRNAs form a pool of metabolically inactive molecules,
at best. At worst, d-aminoacylated tRNAs infiltrate the protein
synthesis machinery. Although the latter harmful possibility has not yet been
firmly established, several cells were shown to possess a
d-tyrosyl-tRNA deacylase, or DTD, that should help them counteract
the accumulation of d-aminoacyl-tRNAs. This enzyme shows a broad
specificity, being able to remove various d-aminoacyl moieties from
the 3′-end of a tRNA
(4–6,
11). Such a function makes the
deacylase a member of the family of enzymes capable of editing in
trans mis-aminoacylated tRNAs. This family includes several homologs
of aminoacyl-tRNA synthetase editing domains
(12), as well as peptidyl-tRNA
hydrolase (13,
14).Two distinct deacylases have already been discovered. The first one, called
DTD1, is predicted to occur in most bacteria and eukaryotes (see
d-amino acids, including
d-tyrosine (6). In
fact, in an E. coli Δdtd strain grown in the presence
of 2.4 mm d-tyrosine, as much as 40% of the cellular
tRNATyr pool becomes esterified with d-tyrosine
(10).
Open in a separate windowHomologs of dtd/DTD1 are not found in the available archaeal
genomes except that of Methanosphaera stadtmanae. A search for
deacylase activity in Sulfolobus solfataricus and Pyrococcus
abyssi led to the detection of another enzyme (DTD2), completely
different from the DTD1 protein
(15). Importing dtd2
into E. coli functionally compensates for dtd deprivation.
As shown in 16).Several cells contain neither dtd nor dtd2 homologs
(d-tyrosyl-tRNA deacylase
(DTD3). This protein, encoded by dtd3, behaves as a metalloenzyme.
Sensitivity of the growth of Synechocystis to external
d-tyrosine is strongly exacerbated by the disruption of
dtd3. Moreover, expression of the Synechocystis DTD3 in a
Δdtd E. coli strain, from a plasmid, restores the resistance of
the bacterium to d-tyrosine. Finally, using the available genomes,
we examined the occurrence of DTD3 in the living world. The prevalence of
DTD3-like proteins is surprisingly high. It suggests that the defense of
protein synthesis against d-amino acids is universal. 相似文献
TABLE 1
Distribution of DTD1 and DTD2 homologs in various phylogenetic groupsHomologs of DTD1 and DTD2 were searched for using a genomic Blast analysis against complete genomes in the NCBI Database (www.ncbi.nlm.nih.gov). Values in the table are number of species. For instance, E. coli is counted only once in γ-proteobacteria despite the fact that several E. coli strains have been sequenced.DTD1 | DTD2 | DTD1 + DTD2 | None | |
---|---|---|---|---|
Bacteria | ||||
Acidobacteria | 2 | 0 | 0 | 0 |
Actinobacteria | 27 | 0 | 0 | 8 |
Aquificae | 1 | 0 | 0 | 0 |
Bacteroidetes/Chlorobi | 12 | 0 | 0 | 5 |
Chlamydiae | 1 | 0 | 0 | 6 |
Chloroflexi | 4 | 0 | 0 | 0 |
Cyanobacteria | 5 | 0 | 0 | 16 |
Deinococcus/Thermus | 4 | 0 | 0 | 0 |
Firmicutes | ||||
Bacillales | 19 | 0 | 0 | 0 |
Clostridia | 19 | 0 | 0 | 0 |
Lactobacillales | 23 | 0 | 0 | 0 |
Mollicutes | 0 | 0 | 0 | 15 |
Fusobacteria/Planctomycetes | 2 | 0 | 0 | 0 |
Proteobacteria | ||||
α | 6 | 0 | 0 | 55 |
β | 24 | 0 | 0 | 11 |
γ | 80 | 0 | 0 | 8 |
δ | 15 | 0 | 0 | 0 |
ε | 1 | 0 | 0 | 12 |
Spirochaetes | 0 | 0 | 0 | 7 |
Thermotogae | 5 | 0 | 0 | 0 |
Archaea | ||||
Crenarchaeota | 0 | 13 | 0 | 0 |
Euryarchaeota | 1 | 26 | 0 | 2 |
Nanoarchaeota | 0 | 0 | 0 | 1 |
Eukaryota | ||||
Dictyosteliida | 1 | 0 | 0 | 0 |
Fungi/Metazoa | ||||
Fungi | 13 | 0 | 0 | 1 |
Metazoa | 19 | 0 | 0 | 0 |
Kinetoplastida | 3 | 0 | 0 | 0 |
Viridiplantae | 4 | 4 | 4 | 0 |
4.
Dynamic changes in cytosolic and nuclear Ca2+ concentration are reported to play a critical regulatory role in different aspects of skeletal muscle development and differentiation. Here we review our current knowledge of the spatial dynamics of Ca2+ signals generated during muscle development in mouse, rat, and Xenopus myocytes in culture, in the exposed myotome of dissected Xenopus embryos, and in intact normally developing zebrafish. It is becoming clear that subcellular domains, either membrane-bound or otherwise, may have their own Ca2+ signaling signatures. Thus, to understand the roles played by myogenic Ca2+ signaling, we must consider: (1) the triggers and targets within these signaling domains; (2) interdomain signaling, and (3) how these Ca2+ signals integrate with other signaling networks involved in myogenesis. Imaging techniques that are currently available to provide direct visualization of these Ca2+ signals are also described.The recognition of Ca2+ as a key regulator of muscle contraction dates back to Sydney Ringer''s seminal observations in the latter part of the 19th Century (Ringer 1883; Ringer 1886; Ringer and Buxton 1887; see reviews by Martonosi 2000; Szent-Györgyi 2004). More recently, evidence is steadily accumulating to support the proposition that Ca2+ also plays a necessary and essential role in regulating embryonic muscle development and differentiation (Flucher and Andrews 1993; Ferrari et al. 1996; Lorenzon et al. 1997; Ferrari and Spitzer 1998, 1999; Wu et al. 2000; Powell et al. 2001; Jaimovich and Carrasco 2002; Li et al. 2004; Brennan et al. 2005; Harris et al. 2005; Campbell et al. 2006; Terry et al. 2006; Fujita et al. 2007; and see reviews by Berchtold et al. 2000; Ferrari et al. 2006; Al-Shanti and Stewart 2009). What is currently lacking, however, is extensive direct visualization of the spatial dynamics of the Ca2+ signals generated by developing and differentiating muscle cells. This is especially so concerning in situ studies. The object of this article, therefore, is to review and report the current state of our understanding concerning the spatial nature of Ca2+ signaling during embryonic muscle development, especially from an in vivo perspective, and to suggest possible directions for future research. The focus of our article is embryonic skeletal muscle development because of this being an area of significant current interest. Several of the basic observations reported, however, may also be common to cardiac muscle development and in some cases to smooth muscle development. What the recent development of reliable imaging techniques has most certainly done, is to add an extra dimension of complexity to understanding the roles played by Ca2+ signaling in skeletal muscle development. For example, it is clear that membrane-bound subcellular compartments, such as the nucleus (Jaimovich and Carrasco 2002), may have endogenous Ca2+ signaling activities, as do specific cytoplasmic domains, such as the subsarcolemmal space (Campbell et al. 2006). How these Ca2+ signals interact with specific down-stream targets within their particular domain, and how they might serve to communicate information among domains, will most certainly be one of the future challenges in elucidating the Ca2+-mediated regulation of muscle development.Any methodology used to study the properties of biological molecules and how they interact during development should ideally provide spatial information, because researchers increasingly need to integrate data about the interactions that underlie a biological process (such as differentiation) with information regarding the precise location within cells or an embryo where these interactions take place. Current Ca2+ imaging techniques are beginning to provide us with this spatial information, and are thus opening up exciting new avenues of investigation in our quest to understand the signaling pathways that regulate muscle development (Animal Intact animals/Cells in culture Ca2+ reporter Reporter Loading Protocol Reference Rat 1° cultures prepared from hind limb muscle of neonatal rat pups Fluo 3-AM Cells incubated in 5.4 µM reporter for 30 min at 25°C. Jaimovich et al. 2000 Mouse Myotubes grown from C2C12 subclone of the C2 mouse muscle cell line Fluo 3-AM Incubated in 5 µM reporter plus 0.1% pluronic F-127 for 1 h at r.t. Flucher and Andrews 1993 Myotubes isolated from the intercostal muscles of E18 wild-type and RyR type 3-null mice. Fluo 3-AM Cells incubated with 4 µM for 30 min at r.t. Conklin et al. 1999b Myotubes in culture prepared from newborn mice. Fluo 3-AM Cells incubated in 10 µM for 20 min. Shirokova et al. 1999 1° cultures prepared from hind limb muscle from newborn mice. Fluo 3-AM Cells incubated in 5.4 µM reporter for 30 min at 25°C. Powell et al. 2001 Embryonic day 18 (E18) isolated diaphragm muscle fibers Fluo 4-AM Incubated in 10 µM reporter for 30 min. Chun et al. 2003 Chick Myotubes prepared from leg or breast of 11-day chick embryos Fluo 3-AM Incubated in 5 µM reporter plus 0.1% pluronic F-127 for 1 h at r.t. Flucher and Andrews 1993 Myoblasts isolated from thigh muscle of E12 embryos. Fluo 3-AM 1 mM stock was diluted 1:200 with 0.2% pluronic F-127. Cells were incubated for 60 min at r.t. in the dark. Tabata et al. 2006 Xenopus Exposed myotome in dissected embryo Fluo-3 AM Incubated dissected tissue in 10 µM reporter for 30–60 min. Ferrari and Spitzer 1999 1° myocyte cultures prepared from stage 15 Xenopus embryos. Fluo-4 AM Cells incubated in 2 µM reporter plus 0.01% pluronic F-127 for 60 min. Campbell et al. 2006 Zebrafish Intact animals Calcium green-1 dextran (10S) Reporter at 20 mM was injected into a single blastomere between the 32- and 128-cell stage. Zimprich et al. 1998 Intact animals Oregon Green 488 BAPTA dextran Single blastomeres from 32-cell stage embryos injected with reporter (i.c. 100 µM) and tetramethylrhodamine dextran (i.c. 40 µM). Ashworth et al. 2001 Intact animals Oregon Green 488 BAPTA dextran Microinjected with rhodamine dextran to give an intracellular concentration of ∼40 µM. Ashworth 2004 Intact animals Aequorin aEmbryos injected with 700 pg aeq-mRNA at the 1-cell stage and then incubated with 50 µM f-coelenterazine from the 64-cell stage. Cheung et al. 2006 Intact animals Aequorin Transgenic fish that express apoaequorin in the skeletal muscles were incubated with 50 µM f-coelenterazine from the 8-cell stage. Cheung et al. 2010