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1.
Sea ice occurs abundantly at the polar caps of the Earth and, probably, of many other planets. Its static and dynamic properties
that may be important for prebiotic and early biotic reactions are described. It concentrates substrates and has many features
that are important for catalytical actions. We propose that it provided optimal conditions for the early replication of nucleic
acids and the RNA world. We repeated a famous prebiotic experiment, the poly-uridylic acid-instructed synthesis of polyadenylic
acid from adenylic acid imidazolides in artificial sea ice, simulating the dynamic variability of real sea ice by cyclic temperature
variation. Poly(A) was obtained in high yield and reached nucleotide chain lengths up to 400 containing predominantly 3′→
5′ linkages. 相似文献
2.
The high efficiency of protein deposition during the neonatal period is driven by high rates of protein synthesis, which are
maximally stimulated after feeding. In the current study, we examined the individual roles of amino acids and insulin in the
regulation of protein synthesis in peripheral and visceral tissues of the neonate by performing pancreatic glucose–amino acid
clamps in overnight-fasted 7-day-old pigs. We infused pigs (n = 8–12/group) with insulin at 0, 10, 22, and 110 ng kg−0.66 min−1 to achieve ~0, 2, 6 and 30 μU ml−1 insulin so as to simulate below fasting, fasting, intermediate, and fed insulin levels, respectively. At each insulin dose,
amino acids were maintained at the fasting or fed level. In conjunction with the highest insulin dose, amino acids were also
allowed to fall below the fasting level. Tissue protein synthesis was measured using a flooding dose of l-[4-3H] phenylalanine. Both insulin and amino acids increased fractional rates of protein synthesis in longissimus dorsi, gastrocnemius,
masseter, and diaphragm muscles. Insulin, but not amino acids, increased protein synthesis in the skin. Amino acids, but not
insulin, increased protein synthesis in the liver, pancreas, spleen, and lung and tended to increase protein synthesis in
the jejunum and kidney. Neither insulin nor amino acids altered protein synthesis in the stomach. The results suggest that
the stimulation of protein synthesis by feeding in most tissues of the neonate is regulated by the post-prandial rise in amino
acids. However, the feeding-induced stimulation of protein synthesis in skeletal muscles is independently mediated by insulin
as well as amino acids. 相似文献
3.
In maturing seed cells, proteins that accumulate in the protein storage vacuoles (PSVs) are synthesized on the endoplasmic reticulum (ER) and transported by vesicles to the PSVs. Vacuolar sorting determinants (VSDs) which are usually amino acid sequences of short or moderate length direct the proteins to this pathway. VSDs identified so far are classified into two types: sequence specific VSDs (ssVSDs) and C-terminal VSDs (ctVSDs). We previously demonstrated that VSDs of α′ and β subunits of β-conglycinin, one of major storage proteins of soybean (Glycine max), reside in the C-terminal ten amino acids. Here we show that both types of VSDs coexist within this region of the α′ subunit. Although ctVSDs can function only at the very C-termini of proteins, the C-terminal ten amino acids of α′ subunit directed green fluorescent protein (GFP) to the PSVs even when they were placed at the N-terminus of GFP, indicating that an ssVSD resides in the sequence. By mutation analysis, it was found that the core sequence of the ssVSD is Ser-Ile-Leu (fifth to seventh residues counted from the C-terminus) which is conserved in the α and β subunits and some vicilin-like proteins. On the other hand, the sequence composed of the C-terminal three amino acids (AFY) directed GFP to the PSVs when it was placed at the C-terminus of GFP, though the function as a VSD was disrupted at the N-terminus of GFP, indicating that the AFY sequence is a ctVSD. 相似文献
4.
We describe the cloning and analysis of mRPA1, the cDNA encoding the largest subunit (RPA194) of murine RNA polymerase I. The coding region comprises an open reading frame
of 5151 bp that encodes a polypeptide of 1717 amino acids with a calculated molecular mass of 194 kDa. Alignment of the deduced
protein sequence reveals homology to the β′ subunit of Escherichia coli RNA polymerase in the conserved regions a-h present in all large subunits of RNA polymerases. However, the overall sequence
homology among the conserved regions of RPA1 from different species is significantly lower than that observed in the corresponding β′-like subunits of class II and III
RNA polymerase. We have raised two types of antibodies which are directed against the conserved regions c and f of RPA194.
Both antibodies are monospecific for RPA194 and do not cross-react with subunits of RNA polymerase II or III. Moreover, these
antibodies immunoprecipitate RNA polymerase I both from murine and human cell extracts and, therefore, represent an invaluable
tool for the identification of RNA polymerase I-associated proteins.
Received: 27 January 1997 / Accepted: 1 April 1997 相似文献
5.
C. Pacot-Hiriart O. Le Gall T. Candresse R. P. Delbos J. Dunez 《Plant cell reports》1999,19(2):203-209
Tomato black ring virus (TBRV) belongs to the nepoviruses, an important genus of phytoviruses characterized by isometric
particles and by their transmission by longidorid nematodes. As for all other nepoviruses, the coat protein (CP) of TBRV is
encoded by the 3′ terminal part of the viral RNA2 (positions 2801–4334). A hybrid gene driving the expression of a truncated
form of the TBRV CP was constructed. It contains a frameshift deletion at position T4065 so that in the encoded protein the last 90 amino acids of the wild-type CP are replaced by 52 amino acids encoded by a different
reading frame of the viral RNA. This hybrid gene was introduced into the genome of Nicotiana tabacum cv 'Xanthi' plants. When compared to control plants, progeny of some transformants expressing the mutated CP gene (CPm+ plants)
showed resistance against TBRV infection. This resistance is characterized by a delay in the appearance of symptoms, a reduction
in the number of infected plants and a reduction in virus accumulation.
Received: 28 February 1997 / Revision received: 1 August 1997 / Accepted: 24 March 1999 相似文献
6.
Cloning, sequencing and expression of cDNA encoding growth hormone from Indian catfish (Heteropneustes fossilis) 总被引:2,自引:0,他引:2
A tissue-specific cDNA library was constructed using polyA+ RNA from pituitary glands of the Indian catfishHeteropneustes fossilis (Bloch) and a cDNA clone encoding growth hormone (GH) was isolated. Using polymerase chain reaction (PCR) primers representing
the conserved regions of fish GH sequences the 3′ region of catfish GH cDNA (540 bp) was cloned by random amplification of
cDNA ends and the clone was used as a probe to isolate recombinant phages carrying the full-length cDNA sequence. The full-length
cDNA clone is 1132 bp in length, coding for an open reading frame (ORF) of 603 bp; the reading frame encodes a putative polypeptide
of 200 amino acids including the signal sequence of 22 amino acids. The 5′ and 3′ untranslated regions of the cDNA are 58
bp and 456 bp long, respectively. The predicted amino acid sequence ofH. fossils GH shared 98% homology with other catfishes. Mature GH protein was efficiently expressed in bacterial and zebrafish systems
using appropriate expression vectors. The successful expression of the cloned GH cDNA of catfish confirms the functional viability
of the clone. 相似文献
7.
Radioactive amino acids, when added to isolated pea chloroplasts or chloroplast extracts engaged in protein synthesis, are incorporated into Rubisco large subunits that co-migrate with native Rubisco during nondenaturing electrophoresis. We have added the transition state analog 2′-carboxyarabinitol bisphosphate (CABP) to chloroplast extracts after in organello or in vitro incorporation of radioactive amino acids into Rubisco large subunits. Upon addition of CABP the radioactive bands co-migrating with native Rubisco undergo a readily detected shift in electrophoretic mobility just as the native enzyme, thus demonstrating the ability of the newly assembled molecules to interact with this transition state analog. 相似文献
8.
Summary. Glutamate increases the extracellular adenosine levels, an important endogenous neuromodulator. The neurotoxicity induced
by glutamate increases the ecto-5′-nucleotidase activity in neurons, which produces adenosine from AMP. L- and D-aspartate
(Asp) mimic most of the actions of glutamate in the N-methyl-D-aspartate (NMDA) receptors. In the present study, both amino
acids stimulated the ecto-5′-nucleotidase activity in cerebellar granule cells. MK-801 and AP-5 prevented the L- and D-Asp-evoked
activation of ecto-5′-nucleotidase. Both NMDA receptor antagonists prevented completely the damage induced by L-Asp, but partially
the D-Asp-induced damage. The antagonist of adenosine A2A receptors (ZM 241385) prevented totally the L- Asp-induced cellular death, but partially the neurotoxicity induced by D-Asp
and the antagonist of adenosine A1 receptors (CPT) had no effect. The results indicated a different involvement of NMDA receptors on the L- or D-Asp-evoked
activation of ecto-5′-nucleotidase and on cellular damage. The adenosine formed from ecto-5′-nucleotidase stimulation preferentially
acted on adenosine A2A receptor which is probably co-operating with the neurotoxicity induced by amino acids. 相似文献
9.
The biosynthesis of fatty acids from [l-14C]-acetate in the chicken liver slicesin vitro was inhibited by cAMP, adenosine, 5′-AMP, 3′-AMP, ATP, NAD and FAD but not by adenine, guanine or inosine. The minimum structural
requirement for inhibition appears to be adenosine. The inhibitory action of adenosine, 5′-AMP and NAD on fatty acid synthesis
is likely to be mediated by adenosine or its metabolites since adenosine deaminase reverses the inhibition while it has no
effect on the inhibition by cAMP; thus, the inhibitory effect of cAMP is probably not mediated through its hydrolysis products,
5′-AMP, or adenosine. 相似文献
10.
K. Makinen E. Generozov N. Arshava A. Kaloshin S. Morozov S. Zavriev 《Molecular Biology》2000,34(2):291-296
A new RNA of about 900 nt was found in the virions of cocksfoot mottle virus (CfMV) and in infected plants by RNA hybridization
and RT-PCR. Structural features suggested that this RNA is a defective interfering RNA (diRNA). The CfMV diRNA was shown to
consist of a 35-nt 5′-terminal genomic region, which formed a hairpin, and a 3′-terminal genomic region, which included the
coat protein (CP) gene lacking the first 120 nt.In vitro translation of the diRNA started at the third Met codon to produce truncated CP. The CfMV diRNA was assumed totrans-activate synthesis of the CP subgenomic RNA (sgRNA). 相似文献
11.
Ornithine decarboxylase (ODC) degrades in proteasome in a ubiquitin-independent manner with the half life of approximately
2 h. Thirty seven C-terminal amino acids of this enzyme constitute a fragment known as the degradation signal (degron), which
is responsible for the effectiveness of protein degradation. Among these amino acids, the key positions have recently been
mapped (Cys441 and Ala442). Mutations of the key amino acids led to ODC general stabilization, whereas substitution of other
amino acids had no significant influence on the ODC degron activity. In addition, deletions or insertions into the region
located between the key amino acids and ODC C-end diminished significantly the rate of protein degradation; hence, the distance
(remoteness) of these amino acids from ODC C-end is, probably, of crucial importance. Taking into account these data, we have
introduced the key amino acids that determine ODC-degron activity into alpha-fetoprotein with the truncated export signal
(ΔAFP) so that their positioning was 20 amino-acid away from the C-end (ΔAFPCAG and ΔAFPLCAG). Secretion of ΔAFP and the modified
proteins from cells was impossible because of a removal of the N-terminal export signal. Computer analysis of ΔAFP and the derivative ΔAFPCAG and ΔAFPLCAG revealed no significant changes
in protein hydrophobicity or in the secondary structure of C-terminal region. The in vitro experiments on HEK293T cells using
MG132 proteasome inhibitor and translation inhibitor cycloheximide have demonstrated similar stability of ΔAFP and the derivative
ΔAFPCAG and ΔAFPLCAG in cells. Thus, introduction of the key amino acids of ODC degron at the key positions relative to the
C-end of ΔAFP did not change the parameters of protein degradation. Perhaps, some other still unknown amino acids are important
for ODC-degron functioning. It may well be that ΔAFP conformation prevents interaction of the protein C-end with proteasome. 相似文献
12.
The Uba2 and Ufd1 proteins of Saccharomyces cerevisiae interact with poly(A) polymerase and affect the polyadenylation activity of cell extracts 总被引:2,自引:0,他引:2
Poly(A) polymerase is responsible for the addition of the adenylate tail to the 3′ ends of mRNA. Using the two-hybrid system,
we have identified two proteins which interact specifically with the Saccharomyces cerevisiae poly(A) polymerase, Pap1. Uba2 is a homolog of ubiquitin-activating (E1) enzymes and Ufd1 is a protein whose function is probably
also linked to the ubiquitin-mediated protein degradation pathway. These two proteins interact with Pap1 and with each other,
but not with eight other target proteins which were tested in the two-hybrid system. The last 115 amino acids of Uba2, which
contains an 82-amino acid region not present in previously characterized E1 enzymes, is sufficient for the interaction with
Pap1. Both Uba2 and Ufd1 can be co-immunoprecipitated from extracts with Pap1, confirming in vitro the interaction identified
by two-hybrid analysis. Depletion of Uba2 from cells produces extracts which polyadenylate precursor RNA with increased efficiency
compared to extracts from nondepleted cells, while depletion of Ufd1 yields extracts which are defective in processing. These
two proteins are not components of polyadenylation factors, and instead may have a role in regulating poly(A) polymerase activity.
Received: 6 January 1997 / Accepted: 27 February 1997 相似文献
13.
The gene encoding a cuticle-degrading serine protease was cloned from three isolates of Lecanicillium psalliotae (syn. Verticillium psalliotae) by 3′ and 5′ RACE (rapid amplification of cDNA ends) method. The gene encodes for 382 amino acids and the protein shares
conserved motifs with subtilisin N and peptidase S8. Comparison of translated cDNA sequences of three isolates revealed one
amino acid polymorphism at position 230. The deduced protease sequence shared high degree of similarities to other cuticle-degrading
proteases from other nematophagous fungi. 相似文献
14.
Da Xiong Han Hai Yan Wang Zhi Liang Ji An Fu Hu Yu Fen Zhao 《Journal of molecular evolution》2010,70(6):572-582
Phosphorylation has to have been one of the key events in prebiotic evolution on earth. In this article, the emergence of
phosphoryl amino acid 5′-nucleosides having a P–N bond is described as a model of the origin of amino acid homochirality and
Genetic Code. It is proposed that the intramolecular interaction between the nucleotide base and the amino acid side-chain
influences the stability of particular amino acid 5′-nucleotides, and the interaction also selects for the chirality of amino
acids. The differences between l- and d-conformation energies (ΔE
conf) are evaluated by DFT methods at the B3LYP/6-31G(d) level. Although, as expected, these ΔE
conf values are not large, they do give differences in energy that can distinguish the chirality of amino acids. Based on our
calculations, the chiral selection of the earliest amino acids for l-enantiomers seems to be determined by a clear stereochemical/physicochemical relationship. As later amino acids developed
from the earliest amino acids, we deduce that the chirality of these late amino acids was inherited from that of the early
amino acids. This idea reaches far back into evolution, and we hope that it will guide further experiments in this area. 相似文献
15.
InPenaeus vannamei, α-amylase is the most important glucosidase and is present as at least two major isoenzymes which have been purified. In
order to obtain information on their structure, a hepatopancreas cDNA library constructed in phage lambda-Zap II (Strategene)
was screened using a synthetic oligonucleotide based on the amino acid sequence of a V8 staphylococcal protease peptide ofP. vannamei α-amylase. Three clones were selected: AMY SK 37 (EMBL sequence accession number: X 77318) is the most complete of the analyzed
clones and was completely sequenced. It contains the complete cDNA sequence coding for one of the major isoenzymes of shrimp
amylase. The deduced amino acid sequence shows the existence of a 511-residue-long pre-enzyme containing a highly hydrophobic
signal peptide of 16 amino acids. Northern hybridization of total RNA with the amylase cDNA confirms the size of the messenger
at around 1,600 bases. AMY SK 28, which contains the complete mature sequence of amylase, belonged to the same family characterized
by a common 3′ terminus and presented four amino acid changes. Some other variants of this family were also partially sequenced.
AMY SK 20 was found to encode a minor variant of the protein with a different 3′ terminus and 57 amino acid changes.
Phylogenetic analysis established with the conserved amino acid regions of the (β/α) eight-barrel domain and with the total
sequence ofP. vannamei showed close evolutionary relationships with mammals (59–63% identity) and with insect α-amylase (52–62% identity). The use
of conserved sequences increased the level of similarity but it did not alter the ordering of the groupings. Location of the
secondary structure elements confirmed the high level of sequence similarity of shrimp α-amylase with pig α-amylase.
Correspondence to: A. Van Wormhoudt 相似文献
16.
17.
We have previously reported the graft transmission of target specificity for RNA silencing using transgenic Nicotiana benthamiana plants expressing the coat protein gene (CP, including the 3′ non-translated region) of Sweet potato feathery mottle virus. Transgenic plants carrying the 5′ 200 and 400 bp regions of CP were newly produced. From these plants, two silenced and two non-silenced lines were selected to investigate the manifestation of transitive RNA silencing by graft experiments. Non-silenced scions carrying the entire transgene were grafted onto either 5′ or 3′ silencing inducer rootstocks. When non-silenced scions were grafted onto 5′ silencing inducer rootstocks, RNA silencing was induced in the non-silenced scions and spread toward the 3′ region of the transgene mRNA. Similarly, when non-silenced scions were grafted onto 3′ silencing inducer rootstocks, RNA silencing was induced in the non-silenced scions, but was restricted to the 3′ region of the transgene and did not spread to the 5′ region. In addition, results from crossing experiments, involving non-silenced and 3′ silencing inducer plants, confirmed the above finding. This indicates that RNA silencing spreads in the 5′–3′ direction, not in the 3′–5′ direction, along the transgene mRNA. 相似文献
18.
By combining crystallographic and NMR structural data for RNA-bound amino acids within riboswitches, aptamers, and RNPs, chemical
principles governing specific RNA interaction with amino acids can be deduced. Such principles, which we summarize in a “polar
profile”, are useful in explaining newly selected specific RNA binding sites for free amino acids bearing varied side chains
charged, neutral polar, aliphatic, and aromatic. Such amino acid sites can be queried for parallels to the genetic code. Using
recent sequences for 337 independent binding sites directed to 8 amino acids and containing 18,551 nucleotides in all, we
show a highly robust connection between amino acids and cognate coding triplets within their RNA binding sites. The apparent
probability (P) that cognate triplets around these sites are unrelated to binding sites is ≅5.3 × 10−45 for codons overall, and P ≅ 2.1 × 10−46 for cognate anticodons. Therefore, some triplets are unequivocally localized near their present amino acids. Accordingly,
there was likely a stereochemical era during evolution of the genetic code, relying on chemical interactions between amino
acids and the tertiary structures of RNA binding sites. Use of cognate coding triplets in RNA binding sites is nevertheless
sparse, with only 21% of possible triplets appearing. Reasoning from such broad recurrent trends in our results, a majority
(approximately 75%) of modern amino acids entered the code in this stereochemical era; nevertheless, a minority (approximately
21%) of modern codons and anticodons were assigned via RNA binding sites. A Direct RNA Template scheme embodying a credible
early history for coded peptide synthesis is readily constructed based on these observations. 相似文献
19.
Summary Low concentrations ofcycloheximide, sufficient to block net protein synthesis in growing normal and cancer cells, had no effect on protein turnover, i.e. either
the incorporation of labeled amino acids from media lacking other amino acids essential for growth, or the loss to the medium
of amino acids from prelabeled cells. At the concentrations that blocked growth, the rate of amino acid incorporation from
complete medium was reduced to the “quo;turnover level,” i.e. the rate of incorporation seen in amino acid-deficient media.
Protein turnover was inhibited only at higher concentrations of the inhibitor. Qualitatively similar results have been obtained
with puromycin, anisomycin, emetin and tylocerebrine. 相似文献
20.
Molecular cloning and expression analysis of a cytosolic Hsp70 gene from Antarctic ice algae Chlamydomonas sp. ICE-L 总被引:1,自引:0,他引:1
Shenghao Liu Pengying Zhang Bailin Cong Chenlin Liu Xuezheng Lin Jihong Shen Xiaohang Huang 《Extremophiles : life under extreme conditions》2010,14(3):329-337
A cDNA encoding heat shock protein 70 of Antarctic ice algae Chlamydomonas sp. ICE-L (designated as CiHsp70) was identified by RT-PCR and rapid amplification of cDNA ends approaches. The full-length
cDNA of CiHsp70 was 2,232 bp, consisting of a 5′-terminal untranslated region (UTR) of 76 bp, a 3′-terminal UTR of 203 bp
with a poly (A) tail, and an open reading frame of 1,953 bp. The CiHsp70 cDNA encoded a polypeptide of 651 amino acids with
an ATPase domain of 388 amino acids, the substrate peptide binding domain of 246 amino acids and a C-terminus domain of 17
amino acids. The inducible CiHsp70 cDNA was highly homologous to other plant cytosolic Hsp70 genes and clustered together
with green algae and higher plant rather than brown algae, diatom and Cryptophyta. Antarctic ice algae were treated with different
stress conditions and messenger RNA (mRNA) expression levels of CiHsp70 were quantified by quantitative RT-PCR. The results
showed that both cold and heat shock treatments could stimulate CiHsp70 mRNA expression. Meanwhile, CiHsp70 mRNA expression
level increased 2.9-fold in response to UV-B radiation for 6 h, while the expression levels of CiHsp70 were remarkably increased
after removing the UV-B radiation and immediately providing additional 6 h visible light. Furthermore, treating with 62 or
93‰ NaCl for 2 h, CiHsp70 mRNA expression level increased 3.0- and 2.1-fold, respectively. Together, our observations revealed
that CiHsp70 as a molecular chaperone might play an important role in Antarctic ice algae Chlamydomonas sp. ICE-L acclimatizing to polar environment. 相似文献