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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The agonist-induced internalization of several G protein-coupled receptors is an obligatory requirement for their activation of MAPKs. Studies on the relationship between endocytosis of the angiotensin II (Ang II) type 1 receptor (AT1-R) and Ang II-induced ERK1/2 activation were performed in clone 9 (C9) rat hepatic cells treated with inhibitors of endocytosis [sucrose, phenylarsine oxide (PAO), and concanavalin A]. Although Ang II-induced endocytosis of the AT1-R was prevented by sucrose and PAO, and was partially inhibited by concanavalin A, there was no impairment of Ang II-induced ERK activation. However, the specific epidermal growth factor receptor (EGF-R) kinase inhibitor, AG1478, abolished Ang II-induced activation of ERK1/2. Sucrose and PAO also inhibited EGFinduced internalization of the EGF-R in C9 cells, and the inability of these agents to impair EGF-induced ERK activation suggested that the latter is also independent of receptor endocytosis. In COS-7 cells transiently expressing the rat AT1A-R, Ang II also caused ERK activation through EGF-R transactivation. Furthermore, a mutant AT1A-R with truncated carboxyl terminus and impaired internalization retained full ability to activate ERK1/2 in response to Ang II stimulation. These findings demonstrate that Ang II-induced ERK1/2 activation in C9 hepatocytes is independent of both AT1-R and EGF-R endocytosis and is mediated by transactivation of the EGF-R.
Mol Endocrinol 2002 Mar
PMID:Independence of angiotensin II-induced MAP kinase activation from angiotensin type 1 receptor internalization in clone 9 hepatocytes. 1187 20

Previous studies have identified two tissue- and cell-specific, yet functionally redundant, sucrose synthase (SuSy) genes, Sh1 and Sus1, which encode biochemically similar isozymes, SH1 and SUS1 (previously referred to as SS1 and SS2, respectively). Here we report evidence for a third SuSy gene in maize, Sus3, which is more similar to dicot than to monocot SuSys. RNA and/or protein blot analyses on developing kernels and other tissues show evidence of expression of Sus3, although at the lowest steady-state levels of the three SuSy gene products and without a unique pattern of tissue specificity. Immunoblots of sh1sus1-1 embryos that are either lacking or deficient for the embryo-specific SUS1 protein have shown a protein band which we attribute to the Sus3 gene, and may contribute to the residual enzyme activity seen in embryos of the double mutant. We also studied developing seeds of the double mutant sh1sus1-1, which is missing 99.5% of SuSy enzyme activity, for evidence of co-regulation of several genes of sugar metabolism. We found a significant reduction in the steady-state levels of Miniature-1 encoded cell wall invertase2, and Sucrose transporter (Sut) mRNAs in the double mutant, relative to the lineage-related sh1Sus1 and sh1Sus1 kernels. Down-regulation of the Mn1 gene was also reflected in significant reductions in cell wall invertase activity. Co-regulatory changes were not seen in the expression of Sucrose phosphate synthase, UDP-glucose pyrophosphorylase, and ADP-glucose pyrophosphorylase.
Plant Mol Biol 2002 May
PMID:Gene expression studies on developing kernels of maize sucrose synthase (SuSy) mutants show evidence for a third SuSy gene. 1200 96

Rhodnius prolixus oocyte extracts were chromatographed on an ion exchange column in order to purify vitellin (VT). Three VT heterogeneous populations were identified and named VT(1), VT(2), and VT(3) according to their order of elution from the column. The phosphate content of each population was determined, after lipid extraction, and a heterogeneous distribution was found: VT(1) being the less phosphorylated (50 mol P/mol protein) and VT(3) the heavily phosphorylated population (281 mol P/mol protein). Analysis of radioactivity associated with each VT population purified from animals fed with (32)Pi showed the same phosphorylation profile. Due to the fact that vitellogenin is the known precursor of VT, we have also chromatographed 32P-VG in the same way as we purified VT. Only one VG's population was detected and resembled to VT(3) with respect to its elution profile. All VT populations contain the same neutral lipids, but they were heterogeneous with respect to phospholipid composition. VT(1) presents phosphatidylcholine and phosphatidylethanolamine whereas VT(2) and VT(3) also showed cardiolipin and probably phosphatidylserine. Sugar composition of VT(2) and VT(3) includes mannose as the main associated carbohydrate but VT(1) also contains glucose resembling VG. Although VG and VT are similar with respect to the elution profile, their sugar composition is different. These results suggest a post-endocytosis processing on VG molecule. The possible biological function of VT heterogeneous populations is discussed.
Insect Biochem Mol Biol 2002 Jul
PMID:Rhodnius prolixus vitellin is composed of three different populations: comparison with vitellogenin. 1204 87

Prosopis chilensis (Mol.) Stuntz (Algarrobo de Chile) is an important native tree species that can be grown in arid and semiarid regions for wood and forage production and environmental protection. Developing a simple and reliable in vitro protocol for cloning it would enable to improve it genetically. Explants of P. chilensis were taken from 4 months-old plants grown in the greenhouse or from adult trees grown in a natural environment. Nodal segments 1-2 cm long containing an axillary bud were selected from elongating shoots. These cuttings were aseptically cultured on two agar-solid basal media, MS or BTMm, and treated with 0.05 mg L-1 BA and 3 mg L-1 of either IAA, IBA or NAA. Sucrose (3% w/v) was used as carbon source. The percentage of sprouted cuttings and whole plant regeneration as well as its shoot and root length were recorded. Number, length and dry weight of shoots and roots were also measured. Rooting was successful with cuttings taken from young or adult plants, but explants from young plants showed a better response. Culturing in BTMm resulted in significantly greater shoot and root biomass than culturing in MS. Moreover, this response was higher in young explants when IBA was used as growth regulator. This paper reports a simple and effective method to micropropagate P. chilensis from young and adult plants.
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PMID:Micropropagation of Prosopis chilensis (Mol.) Stuntz from young and mature plants. 1205 79

Glucose reacts with the amino groups of protein to form a Schiff base that rearranges to form a ketoamine adduct. These early products eventually undergo irreversible chemical modifications generating advanced glycation end products (AGES). We reacted various sugars and sugar phosphates with bovine serum albumin allowing the formation of Amadori and AGE products. The rates of browning, Amadori and AGE products formed during incubations at 37 and 55 degrees C were compared. The correlation between AGE fluorescence and bitopical (crosslinking) modifications in the protein have been evaluated. Pentoses generated maximum Amadori products. Sugar phosphates were found to be more potent in generating AGEs than free sugars as measured by fluorescence. Though glucose, fructose and glucose-6-P do not generate fluorescence comparable to pentoses, they generate high molecular weight aggregates. In contrast, ribose-5-P, which shows significantly higher AGE and pentosidine fluorescence than the other sugars, did not generate high molecular weight aggregates. We suggest that there may not be a direct correlation between the levels of Amadori products, AGEs and crosslinking.
J Biochem Mol Biol Biophys 2002 Aug
PMID:Amadori product and age formation during nonenzymatic glycosylation of bovine serum albumin in vitro. 1218 38

Sucrose is the cornerstone of higher plant metabolism. Produced by photosynthesis, sucrose is the main substrate for respiration and biosynthesis. The emerging idea is that sucrose may act as regulator of its own metabolism, characterized in particular by a permanent process of degradation and formation. This sucrose turnover may control several important physiological functions. Of particular concern is an energy dependent cycle involving the hexokinase. This report presents an experimental approach to define quantitatively physiological states of suspension-cultured plant cells wih reference to their sucrose content and respiration rate. Sucrose depletion of normal cells incubated in a medium devoid of sugar is measured in vivo using 13C and respiration is simultaneously recorded. Results obtained with sucrose-storing cells and Arabidopsis thaliana show that respiration rate is closely linked to the available sucrose. Sucrose-depleted cells offer a stable model to study the bioenergetics of the process.
Mol Biol Rep 2002
PMID:Sucrose cycling in heterotrophic plant cell metabolism: first step towards an experimental model. 1224 Oct 46

Sucrose octasulfate (SOS) is believed to stimulate fibroblast growth factor (FGF) signaling by binding and stabilizing FGFs. In this report, we show that SOS induces FGF-dependent dimerization of FGF receptors (FGFRs). The crystal structure of the dimeric FGF2-FGFR1-SOS complex at 2.6-A resolution reveals a symmetric assemblage of two 1:1:1 FGF2-FGFR1-SOS ternary complexes. Within each ternary complex SOS binds to FGF and FGFR and thereby increases FGF-FGFR affinity. SOS also interacts with the adjoining FGFR and thereby promotes protein-protein interactions that stabilize dimerization. This structural finding is supported by the inability of selectively desulfated SOS molecules to promote receptor dimerization. Thus, we propose that SOS potentiates FGF signaling by imitating the dual role of heparin in increasing FGF-FGFR affinity and promoting receptor dimerization. Hence, the dimeric FGF-FGFR-SOS structure substantiates the recently proposed "two-end" model, by which heparin induces FGF-FGFR dimerization. Moreover, the FGF-FGFR-SOS structure provides an attractive template for the development of easily synthesized SOS-related heparin agonists and antagonists that may hold therapeutic potential.
Mol Cell Biol 2002 Oct
PMID:Structural basis for activation of fibroblast growth factor signaling by sucrose octasulfate. 1224 95

A total of 14 premenopausal human uteri were transferred within minutes from the operating room to the laboratory on ice. All endometrial sampels were in the early proliferative phase. Portions of leiomyomata and of normal myometrium were examined histologically. Other neoplastic and normal portions were homogenized separately. To obtain the cytosol the filtrate was centrifuged twice at high speed. The cytosol was immediately used for sucrose gradient centrifugation, chromatography electrophoresis, and Scatchard analysis. Measurement of the estradiol binding site concentration was done with the charcoal technique. Protein content of the samples was determined, using bovine serum albumin as the standard. Both leiomyomata and normal human myometrium, in each case from the same tumor-bearing uterus, contained specific estrogen receptors in the cytosol. Their affinities for labeled estradiol and electrophoretic mobility after agar gel electrophoresis were similar. Sucrose gradient sedimentation coefficients and chromatographic patterns after agarose gel filtration were identical. In high salt buffer the (tritiated)-estradiol cytoplasmic binding components sedimented as a 4S peak on sucrose gradient. In low salt medium the (tritiated)-estradiol sedimented at about 4S and 8S. Results are in agreement with those of other authors and are consistent with the clinical observation that leiomyomata are estrogen-sensitive tumors.
J Mol Med 1977 Jan
PMID:Estrogen receptors in normal human myometrium and leiomyoma. 1230 4

The phosphoenolpyruvate transferase system (PTS) is the major pathway by which bacteria import hexose sugars across the plasma membrane. The PTS transfers a phosphoryl group sequentially via several components from the glycolytic intermediate phosphoenolpyruvate (PEP) to the translocated sugar. It is comprised of the two general proteins enzyme I and HPr, and a sugar-specific enzyme II complex. Sugar translocation is through the membrane domain of the enzyme II complex. The enzyme II complex can belong to one of six families based upon sequence similarity, with the sorbose transporter from Klebsiella pneumoniae a member of the mannose family.The structure of the IIB(Sor) domain was solved to 1.75A resolution by molecular replacement. It has a central core of seven parallel beta-strands surrounded by a total of six alpha-helices. Three helices cover the front face, one the back face with the remaining two capping the central beta-sheet at the top and bottom. The catalytic His15 residue is situated on the surface-exposed loop between strand 1 and helix 1. In addition to the features previously observed in the homologous IIB(Lev) domain from Bacillus subtilis we see new features in the IIB(Sor) structure. First, the catalytic His15 side-chain is fixed in a specific conformation by forming a short hydrogen bond with Asp10, which in turn makes a salt-bridge with Arg8. Second, as observed in other phosphoproteins, an arginine residue (Arg12) is well poised to stabilize a phosphoryl group on His15. Third, we see an Asp/His pair reminiscent of that observed in the IIA(Man) domain from Escherichia coli. Finally, docking of IIA(Man) to IIB(Sor) shows that Arg12 in its current conformation is well positioned to assist the subsequent transfer of the phosphoryl group onto the sugar in line with previous mutagenesis studies.
J Mol Biol 2003 Apr 11
PMID:Crystal structure of the IIB(Sor) domain of the sorbose permease from Klebsiella pneumoniae solved to 1.75A resolution. 1266 34

Ribosome assembly in Escherichia coli involves 54 ribosomal proteins and three RNAs. Whereas functional subunits can be reconstituted in vitro from the isolated components, this process requires long incubation times and high temperatures compared with the in vivo situation, suggesting that non-ribosomal factors facilitate assembly in vivo. Here, we show that SrmB, a putative DEAD-box RNA helicase, is involved in ribosome assembly. The deletion of the srmB gene causes a slow-growth phenotype at low temperature. Polysome profile analyses of the corresponding cells reveal a deficit in free 50S ribosomal subunits and the accumulation of a new particle sedimenting around 40S. Analysis of the ribosomal RNA and protein contents of the 40S particle indicates that it represents a large subunit that is incompletely assembled. In particular, it lacks L13, one of the five ribosomal proteins that are essential for the early assembly step in vitro. Sucrose gradient fractionation also shows that, in wild-type cells, SrmB associates with a pre50S particle. From our results, we propose that SrmB is involved in an early step of 50S assembly that is necessary for the binding of L13. This step may consist of a structural rearrangement that, at low temperature, cannot occur without the assistance of this putative RNA helicase.
Mol Microbiol 2003 Jun
PMID:The DEAD-box RNA helicase SrmB is involved in the assembly of 50S ribosomal subunits in Escherichia coli. 1278 53


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