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1.
《Insect Biochemistry》1977,7(1):15-20
When paragonia were incubated for 8 hr in simplified Robb's medium a continuous increase in incorporation of 14C-amino acids into TCA precipitable proteins was found. The increase is linear over the first 2 hr.Copulation provides the stimulus for an alteration in rate of in vitro incorporation: a rapid and clear increase occurs. A similar increase in rate of incorporation of 14C-uridine into RNA and 3H-ethanolamine into ‘paragonial substance’ could be found. The pattern of incorporation of 14C-amino acids into proteins, as determined by polyacrylamide gel electrophoresis, remains qualitatively unaltered. Results from transplantation experiments of single paragonia suggest that the stimulation, at least in part, is neuronal or humoral mediated.In vitro incubations with actinomycin D, under conditions of 90% inhibition, resulted in an increased rate of incorporation of 14C-amino acids into proteins. 相似文献
2.
During imbibition and germination of jack pine seeds, the composition of the total extractable chromatin varied. Relative to DNA, the histone levels decreased as the nonhistone chromosomal proteins (NHCP) increased. New chromosomal proteins were synthesized after 2 days of imbibition as judged by recovery of 14C-amino acids from the major protein fractions. Phosphorylation of histones from 32P-phosphoric acid was detected before the incorporation of 14C-amino acids. In the seed the synthesis and relative changes of chromatin coincided with a fall in total soluble protein and free arginine N. By contrast, adenylate energy charge, free glutamine N and in vitro template activity of chromatin increased during chromatin protein synthesis. When seeds had germinated for 4 days after the start of imbibition more radioactivity, derived from free 14C-amino acids, was recovered from the NHCP than from the histones. The percentage amino acid composition of most histone fractions remained stable, whereas the composition of NHCP changed more with time. The phosphorylation of NHCP was 8- to 41-fold greater than that of the histones. Phosphorylation of histone H4 was not detected at any stage of germination. Correlations between recovery of radioactivity (32P and 14C) from chromosomal proteins and higher adenylate energy charge were positive. 相似文献
3.
Paul P. C. Lin 《Plant Growth Regulation》1985,3(3-4):257-268
Incorporation of L-[U-14C] arginine or L-[U-14C] ornithine into putrescine (Put), spermidine (Spd) and spermine (Spm) in embryonectomized barley seeds (Hordeum vulgare L. cv. Himalaya) was studied following imbition with methylglyoxal-bis (guanylhydrazone) (MGBG) and abscisic acid (ABA). Both radiolabeled amino acids were incorporated into the amines as a result of active polyamine biosynthesis in the seed during imbibition. In the aleurone layer, the Spd and Spn existed mainly in the free form (acid soluble). However about 50% of Put was recovered in conjugated form(s) (acid insoluble). Imbibition with 5 and 10M ABA for 3 days increased the accumulation of the free form of 14C-Put, probably as a result of inhibition (70%) of 14C-Spd accumulation. The ABA treatment showed no significant effect on levels of the conjugated form of Put and Spd. Imbibition with millimolar concentrations of MGBG resulted in (i) abnormal accumulation of the free form of Put and incorporation of 14C-amino acids into the diamine, (ii) progressive inhibition of the accumulation of the free forms of 14C-Spd and Spm, and (iii) reduction of the 14C incorporation into the conjugated forms of Put and Spd. Uptake of 14C-amino acids was not affected by MGBG treatment. The results indicate that MGBG may inhibit not only the synthesis of Spd and Spm, but the catabolism (e.g. oxidation) of Put in the aleurone layer.This paper is published with the approval of the director of the Kentucky Agricultural Experiment Station. 相似文献
4.
Changes in growth parameters, carbon assimilation efficiency, and utilization of 14CO2 assimilate into alkaloids in plant parts were investigated at whole plant level by treatment of Catharanthus roseus with gibberellic acid (GA). Application of GA (1 000 g m−3) resulted in changes in leaf morphology, increase in stem elongation, leaf and internode length, plant height, and decrease
in biomass content. Phenotypic changes were accompanied by decrease in contents of chlorophylls and in photosynthetic capacity.
GA application resulted in higher % of total alkaloids accumulated in leaf, stem, and root. GA treatment produced negative
phenotypic response in total biomass production but positive response in content of total alkaloids in leaf, stem, and roots.
14C assimilate partitioning revealed that 14C distribution in leaf, stem, and root of treated plants was higher than in untreated and variations were observed in contents
of metabolites as sugars, amino acids, and organic acids. Capacity to utilize current fixed 14C derived assimilates for alkaloid production was high in leaves but low in roots of treated plants despite higher content
of 14C metabolites such as sugars, amino acids, and organic acids. In spite of higher availability of metabolites, their utilization
into alkaloid production is low in GA-treated roots. 相似文献
5.
Isotope labeling by residue type (LBRT) has long been an important tool for resonance assignments at the limit where other
approaches, such as triple-resonance experiments or NOESY methods do not succeed in yielding complete assignments. While LBRT
has become less important for small proteins it can be the method of last resort for completing assignments of the most challenging
protein systems. Here we present an approach where LBRT is achieved by adding protonated 14N amino acids that are 13C labeled at the carbonyl position to a medium for uniform deuteration and 15N labeling. This has three important benefits over conventional 15N LBRT in a deuterated back ground: (1) selective TROSY-HNCO cross peaks can be observed with high sensitivity for amino-acid
pairs connected by the labeling, and the amide proton of the residue following the 13C labeled amino acid is very sharp since its alpha position is deuterated, (2) the 13C label at the carbonyl position is less prone to scrambling than the 15N at the α-amino position, and (3) the peaks for the 1-13C labeled amino acids can be identified easily from the large intensity reduction in the 1H-15N TROSY-HSQC spectrum for some residues that do not significantly scramble nitrogens, such as alanine and tyrosine. This approach
is cost effective and has been successfully applied to proteins larger than 40 kDa.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
Stanisław Weidner Dorota Łukaszewicz Ryszard Amarowicz 《Acta Physiologiae Plantarum》2000,22(2):185-193
The influence of abscisic acid (ABA) on the process of polysome formation and synthesis of newly-formed proteins by different
polysome populations was studied. Triticale caryopses were germinated in water or various ABA concentrations for 48 hrs, and
afterwards they were transferred to a solution of 14C-amino acids and germinated for an additional 30 min. Embryos were separated from caryopses, and four polysome populations
were isolated: the FP (free polysomes), MBP (membrane-bound polysomes), CBP (cytoskeleton-bound polysomes) and CMBP (cytoskeleton-membrane-bound
polysomes). ABA retarded both the process of polysome formation and their activity in forming new proteins in vivo in all studied fractions. Participation of polysomes in total ribosomal materials (sub-units, monosomes and polysomes) of
each polysome population in the control sample was as follows: FP — 77; MBP — 72; CBP — 70 and CMBP — 66 %, whereas in sample
treated by ABA (100 μM) it was accordingly: 17; 23; 27 and 28%. The largest population made up FP (in control sample 69%),
participation of MBP was always lower and ranged from about 19 to 30 %. Participation of polysome populations bound with the
cytoskeleton CBP and CMBP, both in control sample as well as in samples treated with 1 and 10 μM ABA solution, was only a
few per cent. It should be noted that when the ABA concentration was higher (100 μM) (process of germination was strongly
inhibited), participation of those two populations (CBP and CMBP) was much increased in embryos, respectively to about 18
and 20 %. In both the control group and in embryonal tissue treated with ABA increasing incorporation of radioactive precursors
to newly-formed proteins in vivo in fractions of polysomes isolated by following buffers: C (FP), C + PTE (MBP), C + Tris (CBP) and buf. U (CMBP) was observed.
It should be noted, that the biggest incorporation of 14C-amino acids into nascent polypeptide chains was found in the last polysome population (CMBP). In the sample treated with
ABA (100 μM) the activity of this fraction (CMBP) in forming new proteins is several times, and in the case of FP dozens of
times, more intense. Increased participation of CBP and CMBP in embryos of triticale caryopses treated with ABA (100 μM) and
the largest incorporation of 14C-amino acids into nascent polypeptide chains synthesised by CMBP, may indicate the important role of proteins formed by polysomes
associated with cytoskeleton in inhibition of germination and seedling growth by ABA. 相似文献
7.
Hefke F Bagaria A Reckel S Ullrich SJ Dötsch V Glaubitz C Güntert P 《Journal of biomolecular NMR》2011,49(2):75-84
We present a computational method for finding optimal labeling patterns for the backbone assignment of membrane proteins and
other large proteins that cannot be assigned by conventional strategies. Following the approach of Kainosho and Tsuji (Biochemistry
21:6273–6279 (1982)), types of amino acids are labeled with 13C or/and 15N such that cross peaks between 13CO(i – 1) and 15NH(i) result only for pairs of sequentially adjacent amino acids of which the first is labeled with 13C and the second with 15N. In this way, unambiguous sequence-specific assignments can be obtained for unique pairs of amino acids that occur exactly
once in the sequence of the protein. To be practical, it is crucial to limit the number of differently labeled protein samples
that have to be prepared while obtaining an optimal extent of labeled unique amino acid pairs. Our computer algorithm UPLABEL
for optimal unique pair labeling, implemented in the program CYANA and in a standalone program, and also available through
a web portal, uses combinatorial optimization to find for a given amino acid sequence labeling patterns that maximize the
number of unique pair assignments with a minimal number of differently labeled protein samples. Various auxiliary conditions,
including labeled amino acid availability and price, previously known partial assignments, and sequence regions of particular
interest can be taken into account when determining optimal amino acid type-specific labeling patterns. The method is illustrated
for the assignment of the human G-protein coupled receptor bradykinin B2 (B2R) and applied as a starting point for the backbone assignment of the membrane protein proteorhodopsin. 相似文献
8.
Changes in the metabolism in vivo of amino acids with the lapse of time after feeding a diet were investigated by measuring the incorporation of 14C into some body components one hour after injection with 14C-amino acid mixture.The incorporation of 14C into protein in the liver and carcass was rather constant, but that into blood sugar, liver glycogen, and lipids in the liver and carcass showed a change with the lapse of time after feeding a 25% casein diet or a protein-free diet. The incorporation of 14C into liver glycogen was stimulated shortly after feeding, but it was reduced at 7 hr, when a large amount of glycogen was still in the liver. On the contrary, the specific activity of blood sugar increased with the lapse of time after feeding. The conversion of 14C-amino acids into lipids in the liver and carcass was stimulated shortly after feeding.The incorporation of 14C into protein was higher in the rats fed the protein-free diet than in those fed the 25% casein diet, and the higher incorporation was partly counterbalanced by the lower incorporation of 14C into lipids and glycogen in the rats fed the protein-free diet. 相似文献
9.
Fatty acid-binding proteins (FABPs) are a family of proteins that modulate the transfer of various fatty acids in the cytosol and constitute a significant portion in many energy-consuming cells. The ligand binding properties and specific functions of a particular type of FABP seem to be diverse and depend on the respective binding cavity as well as the cell type from which this protein is derived. Previously, a novel FABP (lcFABP; lc: Luciola cerata) was identified in the light organ of Taiwanese fireflies. The lcFABP was proved to possess fatty acids binding capabilities, especially for fatty acids of length C14–C18. However, the structural details are unknown, and the structure–function relationship has remained to be further investigated. In this study, we finished the 1H, 15N and 13C chemical shift assignments of 15N/13C-enriched lcFABP by solution NMR spectroscopy. In addition, the secondary structure distribution was revealed based on the backbone N, H, Cα, Hα, C and side chain Cβ assignments. These results can provide the basis for further structural exploration of lcFABP. 相似文献
10.
14C-amino acids were supplied to Platymonas subcordiformis (Wille) Hazen and the incorporation of radioactivity into protein and other compounds was followed. Alanine was rapidly metabolized by both N-limited and N-sufficient cells. Arginine and lysine were metabolized rapidly by N-limited cells, but were sequestered from metabolism in N-sufficient cells. This suggests the existence of two functionally distinct pools; a “metabolic” pool that is rapidly metabolized and preferentially used for incorporation into protein, and a “storage” pool rich in basic amino acids that is sequestered from metabolism. 相似文献
11.
Animals with high metabolic rates are believed to have high rates of carbon and nitrogen isotopic incorporation. We hypothesized
that (1) chronic exposure to cold, and hence an increase in metabolic rate, would increase the rate of isotopic incorporation
of both 13C and 15N into red blood cells; and (2) that the rate of isotopic incorporation into red blood cells would be allometrically related
to body mass. Two groups of sparrows were chronically exposed to either 5 or 22°C and switched from a 13C-depleted C3-plant diet to a more 13C-enriched C4-plant one. We used respirometry to estimate the resting metabolic rate of birds exposed chronically to our two experimental temperatures. The allometric relationship between the rate of 13C incorporation into blood and body mass was determined from published data. The of birds at 5°C was 1.9 times higher than that of birds at 22°C. Chronic exposure to a low temperature did not have an effect
on the rate of isotopic incorporation of 15N save for a very small effect on the incorporation of 13C. The isotopic incorporation rate of 13C was 1.5 times faster than that of 15N. The fractional rate of 13C incorporation into avian blood was allometrically related to body mass with an exponent similar to −1/4. We conclude that
the relationship between metabolic rate and the rate of isotopic incorporation into an animal’s tissues is indirect. It is
probably mediated by protein turnover and thus more complex than previous studies have assumed. 相似文献
12.
T. V. Roslyakova O. V. Molchan A. V. Vasekina E. M. Lazareva A. I. Sokolik V. M. Yurin A. H. de Boer A. V. Babakov 《Russian Journal of Plant Physiology》2011,58(1):24-35
Two barley cultivars (Hordeum vulgare L., cvs. Elo and Belogorskii) differing in salt tolerance were used to study 22Na+ uptake, expression of three isoforms of the Na+/H+ antiporter HvNHX1-3, and the cellular localization of these isoforms in the elongation zone of seedling roots. During short
(1 h) incubation, seedling roots of both cultivars accumulated approximately equal quantities of 22Na+. However, after 24-h incubation the content of 22Na+ in roots of a salt-tolerant variety Elo was 40% lower than in roots of the susceptible variety Belogorskii. The content of
22Na+ accumulated in shoots of cv. Elo after 24-h incubation was 6.5 times lower than in shoots of cv. Belogorskii and it was 4
times lower after the salt stress treatment. The cytochemical examination revealed that three proteins HvNHX1-3 are co-localized
in the same cells of almost all root tissues; these proteins were present in the tonoplast and prevacuolar vesicles. Western
blot analysis of HvNHX1-3 has shown that the content of isoforms in vacuolar membranes increased in response to salt stress
in seedling roots and shoots of both cultivars, although the increase was more pronounced in the tolerant cultivar. The content
of HvNHX1 in the seedlings increased in parallel with the enhanced expression of HvNHX1, whereas the increase in HvNHX2 and HvNHX3 protein content was accompanied by only slight changes in expression of respective
genes. The results provide evidence that salt tolerance of barley depends on plant ability to restrict Na+ transport from the root to the shoot and relies on regulatory pathways of HvNHX1-3 expression in roots and shoots during
salt stress. 相似文献
13.
R. Mitra P. Narahari T. Gopalakrishna C. R. Bhatia 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1976,48(3):145-151
Summary Total nitrogen, amino nitrogen, glutamic acid dehydrogenase (GDH) activity and incorporation of 3H-uridine and 14C-amino acids into RNA and proteins, respectively, were compared in the developing grains of three high-protein stocks (IR-480-5-9, GMPR-51 and Erythroceros) and a high-yielding, medium-protein cultivar IR-8. The above parameters were also independently studied in the developing grains of IR-8 grown at 0, 60 and 120 kgN/ha. In addition, mobilization of nitrogen from flag leaf during kernel development was compared in a separate experiment. Higher protein concentration, both in high-protein stocks and in IR-8 grown at 120 kgN/ha, was associated with increased levels of: soluble amino nitrogen, GDH activity, 3H-uridine and 14C-amino acid incorporation. Significant variation was found among the high protein stocks in mobilization of nitrogen from flag leaf.Research partly supported by International Atomic Energy Agency Research Contract 1035 相似文献
14.
Agnieszka?Sitarska Lukasz?Skora Julia?Klopp Susan?Roest César?Fernández Binesh?Shrestha Alvar?D.?Gossert
For a wide range of proteins of high interest, the major obstacle for NMR studies is the lack of an affordable eukaryotic expression system for isotope labeling. Here, a simple and affordable protocol is presented to produce uniform labeled proteins in the most prevalent eukaryotic expression system for structural biology, namely Spodoptera frugiperda insect cells. Incorporation levels of 80 % can be achieved for 15N and 13C with yields comparable to expression in full media. For 2H,15N and 2H,13C,15N labeling, incorporation is only slightly lower with 75 and 73 %, respectively, and yields are typically twofold reduced. The media were optimized for isotope incorporation, reproducibility, simplicity and cost. High isotope incorporation levels for all labeling patterns are achieved by using labeled algal amino acid extracts and exploiting well-known biochemical pathways. The final formulation consists of just five commercially available components, at costs 12-fold lower than labeling media from vendors. The approach was applied to several cytosolic and secreted target proteins. 相似文献
15.
Khan Z Amini S Bloom JS Ruse C Caudy AA Kruglyak L Singh M Perlman DH Tavazoie S 《Genome biology》2011,12(12):R122
In quantitative mass spectrometry-based proteomics, the metabolic incorporation of a single source of 15N-labeled nitrogen has many advantages over using stable isotope-labeled amino acids. However, the lack of a robust computational
framework for analyzing the resulting spectra has impeded wide use of this approach. We have addressed this challenge by introducing
a new computational methodology for analyzing 15N spectra in which quantification is integrated with identification. Application of this method to an Escherichia coli growth transition reveals significant improvement in quantification accuracy over previous methods. 相似文献
16.
Differential Infection of Polarized Epithelial Cell Lines by Sialic Acid-Dependent and Sialic Acid-Independent Rotavirus Strains 总被引:8,自引:2,他引:6
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Infection of epithelial cells by some animal rotaviruses, but not human or most animal rotaviruses, requires the presence of N-acetylneuraminic (sialic) acid (SA) on the cell surface for efficient infectivity. To further understand how rotaviruses enter susceptible cells, six different polarized epithelial cell lines, grown on permeable filter membrane supports containing 0.4-μm pores, were infected apically or basolaterally with SA-independent or SA-dependent rotaviruses. SA-independent rotaviruses applied apically or basolaterally were capable of efficiently infecting both sides of the epithelium of all six polarized cell lines tested, while SA-dependent rotaviruses only infected efficiently through the apical surface of five of the polarized cell lines tested. Regardless of the route of virus entry, SA-dependent and SA-independent rotaviruses were released almost exclusively from the apical domain of the plasma membrane of polarized cells before monolayer disruption or cell lysis. The transepithelial electrical resistance (TER) of cells decreased at the same time, irrespective of whether infection with SA-independent rotaviruses occurred apically or basolaterally. The TER of cells infected apically with SA-dependent rotaviruses decreased earlier than that of cells infected basolaterally. Rotavirus infection decreased TER before the appearance of cytopathic effect and cell death and resulted in an increase in the paracellular permeability to [3H]inulin as a function of loss of TER. The presence of SA residues on either the apical or basolateral side was determined using a Texas Red-conjugated lectin, wheat germ agglutinin (WGA), which binds SA residues. WGA bound exclusively to SA residues on the apical surface of the cells, confirming the requirement for SA residues on the apical cell membrane for efficient infectivity of SA-dependent rotaviruses. These results indicate that the rotavirus SA-independent cellular receptor is present on both sides of the epithelium, but SA-dependent and SA-independent rotavirus strains infect polarized epithelial cells by different mechanisms, which may be relevant for pathogenesis and selection of vaccine strains. Finally, rotavirus-induced alterations of the epithelial barrier and paracellular permeability suggest that common mechanisms of pathogenesis may exist between viral and bacterial pathogens of the intestinal tract. 相似文献
17.
Summary Various plant secondary products have been implicated in the promotion of good health or the prevention of disease in humans,
but little is known about the way they are absorbed in the gut, or in which tissues they are deposited throughout the body.
While these issues could be studied if the phytochemicals were isotopically labeled, generating labeled molecules often is
problematic because many compounds of interest can be synthesized only in planta at present. In order to generale 14C-labeled phytochemicals of high radioactive enrichment, we developed an enclosed-chamber labeling system in which cell suspension
cultures can be safely and efficiently grown when supplied with 14C-enriched precursors. The system is designed to hold culture flasks within a clear, polyacrylic compartment that is affixed
to the top of a rotary shaker. The flow-through gas exchange nature of the system allows for O2 replenishment and complete capture of respired 14CO2 throughout the entire period of cell culture. Air is circulated internally with the aid of a small fan, and chamber air temperature
is monitored continuously with an internal temperature probe and data logger. Production runs of 12–14 d with Vaccinium pahalae (ohelo berry) and Vitis vinifera (grape) suspension cultures, using [14C]sucrose as the carbon source, demonstrated a 20–23% efficiency of 14C incorporation into the flavonoid-rich fractions. Further studies with ohelo cell cultures showed that flavonoids were produced
with either sucrose or glucose as the carbohydrate source, although flavonoid productivity (measured as anthocyanins) was
higher with sucrose. This comprehensive chamber system should have broad applicability with numerous cell types and can be
used to generate a wide array of labeled phytochemicals. 相似文献
18.
To gain insight into the metabolic design of the amino acid carrier systems in fish, we injected a bolus of 15N amino acids into the dorsal aorta in mature rainbow trout (Oncorhynchus mykiss). The plasma kinetic parameters including concentration, pool size, rate of disappearance (R
d), half-life and turnover rate were determined for 15 amino acids. When corrected for metabolic rate, the R
d values obtained for trout for most amino acids were largely comparable to human values, with the exception of glutamine (which
was lower) and threonine (which was higher). R
d values ranged from 0.9 μmol 100 g−1 h−1 (lysine) to 22.1 μmol 100 g−1 h−1 (threonine) with most values falling between 2 and 6 μmol 100 g−1 h−1. There was a significant correlation between R
d and the molar proportion of amino acids in rainbow trout whole body protein hydrolysate. Other kinetic parameters did not
correlate significantly with whole body amino acid composition. This indicates that an important design feature of the plasma-free
amino acids system involves proportional delivery of amino acids to tissues for protein synthesis. 相似文献
19.
Ulrich Weininger 《Journal of biomolecular NMR》2017,67(1):23-34
Nuclear magnetic resonance spectroscopy studies of ever larger systems have benefited from many different forms of isotope labeling, in particular, site specific isotopic labeling. Site specific 13C labeling of methyl groups has become an established means of probing systems not amenable to traditional methodology. However useful, methyl reporter sites can be limited in number and/or location. Therefore, new complementary site specific isotope labeling strategies are valuable. Aromatic amino acids make excellent probes since they are often found at important interaction interfaces and play significant structural roles. Aromatic side chains have many of the same advantages as methyl containing amino acids including distinct 13C chemical shifts and multiple magnetically equivalent 1H positions. Herein we report economical bacterial production and one-step purification of phenylalanine with 13C incorporation at the Cα, Cγ and Cε positions, resulting in two isolated 1H-13C spin systems. We also present methodology to maximize incorporation of phenylalanine into recombinantly overexpressed proteins in bacteria and demonstrate compatibility with ILV-methyl labeling. Inexpensive, site specific isotope labeled phenylalanine adds another dimension to biomolecular NMR, opening new avenues of study. 相似文献
20.
Bok‐Rye Lee Sowbiya Muneer Kil‐Yong Kim Jean‐Christophe Avice Alain Ourry Tae‐Hwan Kim 《Physiologia plantarum》2013,147(3):369-380
To characterize the mechanisms of amino acid accumulation under sulphur (S)‐deficiency and its physiological significance in Brassica napus, stable isotopes 15N and 34S were employed. The plants were exposed for 9 days to S‐deficient conditions (0.05 mM vs 1.5 mM sulphate). After 9 days of S‐deficiency, leaf‐osmotic potential and total chlorophyll content significantly decreased. S uptake decreased by 94%, whereas N uptake and biomass were not significantly changed. Using 15N and 34S labelling, de novo synthesis of amino acids and proteins derived from newly absorbed NO3? and SO42? and the content of N and S in the previously synthesized amino acids and proteins were quantified. At the whole plant level, S‐deficiency increased the pool of amino acids but resulted in strong decrease of incorporation of newly absorbed NO3? and SO42? into amino acids by 22.2 and 76.6%, respectively, compared to the controls. Total amount of N and S incorporated into proteins also decreased by 28.8 and 62.1%, respectively. The levels of 14N‐ and 32S‐proteins (previously synthesized proteins) strongly decreased, mainly in mature leaves. The data thus indicate that amino acid accumulation under short‐term S‐deficiency results from the degradation of previously synthesized proteins rather than from de novo synthesis. 相似文献