scholarly journals Complete Topographical Distribution of Both thein Vivoandin VitroPhosphorylation Sites of Bone Sialoprotein and Their Biological Implications

2004 ◽  
Vol 279 (19) ◽  
pp. 19808-19815 ◽  
Author(s):  
Erdjan Salih ◽  
Rudolf Flückiger
Keyword(s):  
Solid Phase ◽  
Phosphorylation Site ◽  
Peptide Sequencing ◽  
Bone Sialoprotein ◽  
Phosphorylation Sites ◽  
Flight Mass Spectrometry ◽  
Topographical Distribution ◽  
Thiol Reagent

Bone sialoprotein (BSP) is a multifunctional, highly phosphorylated, and glycosylated protein with key roles in biomineralization and tissue remodeling. This work identifies the complete topographical distribution and precise location of both thein vitroandin vivophosphorylation sites of bovine BSP by a combination of state-of-the-art techniques and approaches. In vitrophosphorylation of native and deglycosylated BSPs by casein kinase II identified seven phosphorylation sites by solid-phase N-terminal peptide sequencing that were within peptides 12–22 (LEDS(P)EENGVFK), 42–62 (FAVQSSSDSS(P)EENGNGDS(P)S(P)EE), 80–91 (EDS(P)DENEDEES(P)E), and 135–145 (EDES(P)DEEEEEE). Thein vivophosphorylation regions and sites were identified by use of a novel thiol reagent, 1-S-mono[14C]carboxymethyldithiothreitol. This approach identified all of the phosphopeptides defined byin vitrophosphorylation, but two additional phosphopeptides were defined at residues, 250–264 (DNGYEIYES(P)ENGDPR), and 282–289 (GYDS(P)YDGQ). Furthermore, use of native BSP and matrix-assisted laser desorption ionization time-of-flight mass spectrometry identified several of the above peptides, including an additional phosphopeptide at residues 125–130 (AGAT(P)GK) that was not defined in either of thein vitroandin vivostudies described above. Overall, 7in vitroand 11in vivophosphorylation sites were identified unequivocally, with natural variation in the quantitative extent of phosphorylation at eachin vivophosphorylation site.

scholarly journals The Arabidopsis Rho of Plants GTPase ROP1 Is a Potential Calcium-Dependent Protein Kinase (CDPK) Substrate

Plants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2053
Author(s):  
Dalma Ménesi ◽  
Éva Klement ◽  
Györgyi Ferenc ◽  
Attila Fehér
Keyword(s):  
Protein Kinases ◽  
Phosphorylation Site ◽  
Interaction Strength ◽  
Yeast Cells ◽  
Phosphorylation Sites ◽  
Mutant Proteins ◽  
In Vivo Test ◽  
Calcium Dependent

Plant Rho-type GTPases (ROPs) are versatile molecular switches involved in a number of signal transduction pathways. Although it is well known that they are indirectly linked to protein kinases, our knowledge about their direct functional interaction with upstream or downstream protein kinases is scarce. It is reasonable to suppose that similarly to their animal counterparts, ROPs might also be regulated by phosphorylation. There is only, however, very limited experimental evidence to support this view. Here, we present the analysis of two potential phosphorylation sites of AtROP1 and two types of potential ROP-kinases. The S74 site of AtROP1 has been previously shown to potentially regulate AtROP1 activation dependent on its phosphorylation state. However, the kinase phosphorylating this evolutionarily conserved site could not be identified: we show here that despite of the appropriate phosphorylation site consensus sequences around S74 neither the selected AGC nor CPK kinases phosphorylate S74 of AtROP1 in vitro. However, we identified several phosphorylation sites other than S74 for the CPK17 and 34 kinases in AtROP1. One of these sites, S97, was tested for biological relevance. Although the mutation of S97 to alanine (which cannot be phosphorylated) or glutamic acid (which mimics phosphorylation) somewhat altered the protein interaction strength of AtROP1 in yeast cells, the mutant proteins did not modify pollen tube growth in an in vivo test.

scholarly journals Rad53 Checkpoint Kinase Phosphorylation Site Preference Identified in the Swi6 Protein of Saccharomyces cerevisiae

2003 ◽  
Vol 23 (10) ◽  
pp. 3405-3416 ◽  
Author(s):  
Julia M. Sidorova ◽  
Linda L. Breeden
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Damage ◽  
Phosphorylation Site ◽  
Site Preference ◽  
Phosphorylation Sites ◽  
Checkpoint Kinase ◽  
Checkpoint Signaling ◽  
And Function

ABSTRACT Rad53 of Saccharomyces cerevisiae is a checkpoint kinase whose structure and function are conserved among eukaryotes. When a cell detects damaged DNA, Rad53 activity is dramatically increased, which ultimately leads to changes in DNA replication, repair, and cell division. Despite its central role in checkpoint signaling, little is known about Rad53 substrates or substrate specificity. A number of proteins are implicated as Rad53 substrates; however, the evidence remains indirect. Previously, we have provided evidence that Swi6, a subunit of the Swi4/Swi6 late-G1-specific transcriptional activator, is a substrate of Rad53 in the G1/S DNA damage checkpoint. In the present study we identify Rad53 phosphorylation sites in Swi6 in vitro and demonstrate that at least one of them is targeted by Rad53 in vivo. Mutations in these phosphorylation sites in Swi6 shorten but do not eliminate the Rad53-dependent delay of the G1-to-S transition after DNA damage. We derive a consensus for Rad53 site preference at positions −2 and +2 (−2/+2) and identify its potential substrates in the yeast proteome. Finally, we present evidence that one of these candidates, the cohesin complex subunit Scc1 undergoes DNA damage-dependent phosphorylation, which is in part dependent on Rad53.

scholarly journals Phosphorylation of GAP-43 T172 is a molecular marker of growing axons in a wide range of mammals including primates

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Masayasu Okada ◽  
Yosuke Kawagoe ◽  
Yuta Sato ◽  
Motohiro Nozumi ◽  
Yuya Ishikawa ◽  
...  
Keyword(s):  
Molecular Marker ◽  
Phosphorylation Site ◽  
Axon Growth ◽  
Growth Cones ◽  
Specific Protein ◽  
Phosphorylation Sites ◽  
Quarter Century ◽  
Wide Range

AbstractGAP-43 is a vertebrate neuron-specific protein and that is strongly related to axon growth and regeneration; thus, this protein has been utilized as a classical molecular marker of these events and growth cones. Although GAP-43 was biochemically characterized more than a quarter century ago, how this protein is related to these events is still not clear. Recently, we identified many phosphorylation sites in the growth cone membrane proteins of rodent brains. Two phosphorylation sites of GAP-43, S96 and T172, were found within the top 10 hit sites among all proteins. S96 has already been characterized (Kawasaki et al., 2018), and here, phosphorylation of T172 was characterized. In vitro (cultured neurons) and in vivo, an antibody specific to phosphorylated T172 (pT172 antibody) specifically recognized cultured growth cones and growing axons in developing mouse neurons, respectively. Immunoblotting showed that pT172 antigens were more rapidly downregulated throughout development than those of pS96 antibody. From the primary structure, this phosphorylation site was predicted to be conserved in a wide range of animals including primates. In the developing marmoset brainstem and in differentiated neurons derived from human induced pluripotent stem cells, immunoreactivity with pT172 antibody revealed patterns similar to those in mice. pT172 antibody also labeled regenerating axons following sciatic nerve injury. Taken together, the T172 residue is widely conserved in a wide range of mammals including primates, and pT172 is a new candidate molecular marker for growing axons.

scholarly journals The relative roles of specific N- and C-terminal phosphorylation sites in the disassembly of intermediate filament in mitotic BHK-21 cells

1996 ◽  
Vol 109 (4) ◽  
pp. 817-826 ◽  
Author(s):  
Y.H. Chou ◽  
P. Opal ◽  
R.A. Quinlan ◽  
R.D. Goldman
Keyword(s):  
Protein Kinase ◽  
Phosphorylation Site ◽  
Supramolecular Organization ◽  
Phosphorylation Sites ◽  
Bhk Cells ◽  
Terminal Domain ◽  
Kinase Phosphorylation ◽  
Mitotic Cells

Previously we identified p34cdc2 as one of two protein kinases mediating the hyperphosphorylation and disassembly of vimentin in mitotic BHK-21 cells. In this paper, we identify the second kinase as a 37 kDa protein. This p37 protein kinase phosphorylates vimentin on two adjacent residues (thr-457 and ser-458) which are located in the C-terminal non-alpha-helical domain. Contrary to the p34cdc2 mediated N-terminal phosphorylation (at ser-55) which can disassemble vimentin intermediate filaments (IF) in vitro, p37 protein kinase phosphorylates vimentin-IF without obviously affecting its structure in vitro. We have further examined the in vivo role(s) of vimentin phosphorylation in the disassembly of the IF network in mitotic BHK cells by transient transfection assays. In untransfected BHK cells, the interphase vimentin IF networks are disassembled into non-filamentous aggregates when cells enter mitosis. Transfection of cells with vimentin cDNA lacking the p34cdc2 phosphorylation site (ser55:ala) effectively prevents mitotic cells from disassembling their IF. In contrast, apparently normal disassembly takes place in cells transfected with cDNA containing mutated p37 kinase phosphorylation sites (thr457:ala/ser458:ala). Transfection of cells with vimentin cDNAs lacking both the N- and C-terminal phosphorylation sites yields a phenotype indistinguishable from that obtained with the single N-terminal mutant. Taken together, our results demonstrate that the site-specific phosphorylation of the N-terminal domain, but not the C-terminal domain of vimentin plays an important role in determining the state of IF polymerization and supramolecular organization in mitotic cells.

scholarly journals Multisite phosphorylation of doublecortin by cyclin-dependent kinase 5

2004 ◽  
Vol 381 (2) ◽  
pp. 471-481 ◽  
Author(s):  
Mark E. GRAHAM ◽  
Patricia RUMA-HAYNES ◽  
Amanda G. CAPES-DAVIS ◽  
Joanne M. DUNN ◽  
Timothy C. TAN ◽  
...  
Keyword(s):  
Phosphorylation Site ◽  
Site Directed Mutagenesis ◽  
Phosphorylation Sites ◽  
Single Mutation ◽  
Cyclin Dependent Kinase ◽  
Major Site ◽  
Multisite Phosphorylation ◽  
Cyclin Dependent Kinase 5

Doublecortin (DCX) is a 40 kDa microtubule-associated protein required for normal neural migration and cortical layering during development. Mutations in the human DCX gene cause a disruption of cortical neuronal migration. Defects in cdk5 (cyclin-dependent kinase 5) also cause defects in neural migration and cortical layering. DCX is a substrate for cdk5 in vitro and in vivo and the major site of in vitro phosphorylation is Ser-297. We used a highly developed MS strategy to identify the cdk5 phosphorylation sites and determine the major and minor sites. Several phosphopeptides were identified from a tryptic digest of 32P-labelled, cdk5-phosphorylated DCX using a combination of off-line HPLC and matrix-assisted laser-desorption ionization-MS with alkaline phosphatase treatment. Tandem MS/MS enabled the identification of seven phosphorylation sites for cdk5. Monitoring of 32P label indicated that there was one major site, Ser-28, at the N-terminus, and a major site, Ser-339, in the serine/proline-rich domain at the C-terminus. Five other sites, Ser-287, Thr-289, Ser-297, Thr-326 and Ser-332, were also found in the tail. Site-directed mutagenesis largely supported these findings. Single mutation of Ser-28 reduced but did not abolish phosphorylation. Double, rather than single, mutation for Ser-332 and Ser-339 was required to reduce overall phosphorylation, suggesting an interaction between these sites. Truncations of the tail produced a significant reduction in cdk5 phosphorylation of DCX. These results do not support Ser-297 as the major cdk5 phosphorylation site in DCX, but indicate that DCX is subject to complex multisite phosphorylation. This illustrates the importance of a well-developed MS strategy to identify phosphorylation sites.

scholarly journals New Metabolites of Udenafil Identified through Liquid Chromatography– Quadrupole Time-of-flight Mass Spectrometry

2020 ◽  
Vol 17 ◽  
Author(s):  
Jaesung Pyo
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Solid Phase ◽  
Liver Microsomes ◽  
Time Of Flight ◽  
Rat Urine ◽  
Flight Mass Spectrometry ◽  
Tof Ms

Background: Udenafil, a recently discovered drug used for erectile dysfunction treatment, has been widely prescribed and its effect on human systems has been extensively studied. However, there is little research on the human metabolites of udenafil. Three metabolites have been identified in rats. Objective: Herein, highly sensitive and accurate liquid chromatography–quadrupole time-of-flight tandem mass spectrometry (LC-Q-TOF-MS/MS) was conducted to identify new udenafil metabolites. Methods: Human liver microsomes were incubated with udenafil for in vitro samples, and rat urine and faeces samples were collected from udenafil-administered rats for in vivo samples. Each sample was deproteinated with acetonitrile and extracted by solid phase extraction. The purified samples were separated and analyzed by LC-Q-TOF-MS, and some metabolite candidates were reanalyzed for further structural analysis using LC-Q-TOF-MS/MS. Results: Eleven and three metabolites were identified in the in vitro and in vivo samples, respectively, and were found to be hydrolyzed, oxidized, or demethylated forms of udenafil or its metabolites. The error of the metabolic analysis was −8.7 to 7.6 ppm, indicating the high accuracy of the method. Conclusion: These metabolic results could be useful for further investigation of udenafil and new phosphodiesterase-5 inhibitors.

scholarly journals Mycobacterium tuberculosis Maltosyltransferase GlgE, a Genetically Validated Antituberculosis Target, Is Negatively Regulated by Ser/Thr Phosphorylation

2013 ◽  
Vol 288 (23) ◽  
pp. 16546-16556 ◽  
Author(s):  
Jade Leiba ◽  
Karl Syson ◽  
Grégory Baronian ◽  
Isabelle Zanella-Cléon ◽  
Rainer Kalscheuer ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Mycobacterium Smegmatis ◽  
Streptomyces Coelicolor ◽  
Phosphorylation Site ◽  
Catalytic Efficiency ◽  
Forward Genetics ◽  
Phosphorylation Sites ◽  
Potential Therapeutic Target

GlgE is a maltosyltransferase involved in the biosynthesis of α-glucans that has been genetically validated as a potential therapeutic target against Mycobacterium tuberculosis. Despite also making α-glucan, the GlgC/GlgA glycogen pathway is distinct and allosterically regulated. We have used a combination of genetics and biochemistry to establish how the GlgE pathway is regulated. M. tuberculosis GlgE was phosphorylated specifically by the Ser/Thr protein kinase PknB in vitro on one serine and six threonine residues. Furthermore, GlgE was phosphorylated in vivo when expressed in Mycobacterium bovis bacillus Calmette–Guérin (BCG) but not when all seven phosphorylation sites were replaced by Ala residues. The GlgE orthologues from Mycobacterium smegmatis and Streptomyces coelicolor were phosphorylated by the corresponding PknB orthologues in vitro, implying that the phosphorylation of GlgE is widespread among actinomycetes. PknB-dependent phosphorylation of GlgE led to a 2 orders of magnitude reduction in catalytic efficiency in vitro. The activities of phosphoablative and phosphomimetic GlgE derivatives, where each phosphorylation site was substituted with either Ala or Asp residues, respectively, correlated with negative phosphoregulation. Complementation studies of a M. smegmatis glgE mutant strain with these GlgE derivatives, together with both classical and chemical forward genetics, were consistent with flux through the GlgE pathway being correlated with GlgE activity. We conclude that the GlgE pathway appears to be negatively regulated in actinomycetes through the phosphorylation of GlgE by PknB, a mechanism distinct from that known in the classical glycogen pathway. Thus, these findings open new opportunities to target the GlgE pathway therapeutically.

68Ga-labeled HBED-CC Variant of uPAR Targeting Peptide AE105 Compared with 68Ga-NODAGA-AE105

2019 ◽  
Vol 18 (9) ◽  
pp. 1289-1294 ◽  
Author(s):  
Kusum Vats ◽  
Rohit Sharma ◽  
Haladhar D. Sarma ◽  
Drishty Satpati ◽  
Ashutosh Dash
Keyword(s):  
Solid Phase ◽  
Evaluation Studies ◽  
Radiochemical Yield ◽  
In Vivo Evaluation ◽  
Peptide Conjugates ◽  
Biodistribution Studies ◽  
Target Organs ◽  
U87mg Tumor

Aims: The urokinase Plasminogen Activator Receptors (uPAR) over-expressed on tumor cells and their invasive microenvironment are clinically significant molecular targets for cancer research. uPARexpressing cancerous lesions can be suitably identified and their progression can be monitored with radiolabeled uPAR targeted imaging probes. Hence this study aimed at preparing and evaluating two 68Ga-labeled AE105 peptide conjugates, 68Ga-NODAGA-AE105 and 68Ga-HBED-CC-AE105 as uPAR PET-probes. Method: The peptide conjugates, HBED-CC-AE105-NH2 and NODAGA-AE105-NH2 were manually synthesized by standard Fmoc solid phase strategy and subsequently radiolabeled with 68Ga eluted from a commercial 68Ge/68Ga generator. In vitro cell studies for the two radiotracers were performed with uPAR positive U87MG cells. Biodistribution studies were carried out in mouse xenografts with the subcutaneously induced U87MG tumor. Results: The two radiotracers, 68Ga-NODAGA-AE105 and 68Ga-HBED-CC-AE105 that were prepared in >95% radiochemical yield and >96% radiochemical purity, exhibited excellent in vitro stability. In vivo evaluation studies revealed higher uptake of 68Ga-HBED-CC-AE105 in U87MG tumor as compared to 68Ga-NODAGAAE105; however, increased lipophilicity of 68Ga-HBED-CC-AE105 resulted in slower clearance from blood and other non-target organs. The uPAR specificity of the two radiotracers was ascertained by significant (p<0.05) reduction in the tumor uptake with a co-injected blocking dose of unlabeled AE-105 peptide. Conclusion: Amongst the two radiotracers studied, the neutral 68Ga-NODAGA-AE105 with more hydrophilic chelator exhibited faster clearance from non-target organs. The conjugation of HBED-CC chelator (less hydrophilic) resulted in negatively charged 68Ga-HBED-CC-AE105 which was observed to have high retention in blood that decreased target to non-target ratios.

Oxytocin analogues with non-coded amino acid residues in position 8: [8-Neopentylglycine]oxytocin and [8-cycloleucine]oxytocin

1987 ◽  
Vol 52 (9) ◽  
pp. 2317-2325 ◽  
Author(s):  
Jan Hlaváček ◽  
Jan Pospíšek ◽  
Jiřina Slaninová ◽  
Walter Y. Chan ◽  
Victor J. Hruby
Keyword(s):  
Amino Acid ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
The Other ◽  
Amino Acid Residues ◽  
Phase Synthesis ◽  
Other Hand ◽  
Fragment Condensation

[8-Neopentylglycine]oxytocin (II) and [8-cycloleucine]oxytocin (III) were prepared by a combination of solid-phase synthesis and fragment condensation. Both analogues exhibited decreased uterotonic potency in vitro, each being about 15-30% that of oxytocin. Analogue II also displayed similarly decreased uterotonic potency in vivo and galactogogic potency. On the other hand, analogue III exhibited almost the same potency as oxytocin in the uterotonic assay in vivo and in the galactogogic assay.

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