Disease relevance of phosphothreonine

• A small fraction of polyoma virus middle-sized tumor (T) antigen is phosphorylated in vivo, resulting in a small amount of phosphotyrosine and phosphothreonine and significantly larger amounts of phosphoserine [1].
• Immunoprecipitation of Sp1 followed by Western blotting with antibodies to O-linked GlcNAc, phosphoserine, and phosphothreonine showed that hyperglycemia increased GlcNAc by 1.7-fold, decreased phosphoserine by 80%, and decreased phosphothreonine by 70% [2].
• The most striking difference was the prominence in the baculovirus map of peptides containing phosphothreonine 124 [3].
• We have found that treatment of human ovary carcinoma (CaOv) cells with vanadate causes the increase in total protein phosphorylation from 1.5- to 2.0-fold whereas the ratio between phosphoserine, phosphothreonine, and phosphotyrosine content remains unchanged [4].
• The position of phosphothreonine in the predicted primary structure of simian virus 40 large T antigen was determined by different methods [5].

High impact information on phosphothreonine

• The lip is refolded, bringing the phosphothreonine and phosphotyrosine into alignment with surface arginine-rich binding sites [6].
• Phosphoserine/phosphothreonine but not phosphotyrosine residues on BCR are required for interaction with the ABL SH2 domain [7].
• The EGF receptor itself is a phosphoprotein containing phosphotyrosine as well as phosphoserine and phosphothreonine [8].
• Phosphoserine- or phosphothreonine-binding activity was required for Pin1 to interact with its substrates in vitro and to perform its essential function in vivo [9].
• The Pin1 WW domain functioned as a phosphoserine- or phosphothreonine-binding module, with properties similar to those of SRC homology 2 domains [9].

Biological context of phosphothreonine

• Using a phosphothreonine 187 site-specific antibody for p27, we show that threonine 187 phosphorylation of p27 is also cell-cycle dependent, being present in proliferating cells but undetectable in G1 cells [10].
• The FHA domain is linked to the kinase/phosphatase catalytic domain by a flexible tether, and it exhibits a mode of target selection based on electrostatic complementarity between the binding surface and the phosphothreonine peptide [11].
• The time course of phosphorylation of peptide 2, which also contained only phosphothreonine, did not parallel the time course of the generation of Ca2+/calmodulin-independence [12].
• Acid hydrolysis of the tryptic peptides revealed 32P-label label comigrating with phosphoserine; some of it, however, was also identified as phosphothreonine [13].
• Different SH2 domains exhibit distinct binding specificities for both phosphotyrosine- and phosphoserine/phosphothreonine-containing proteins [14].

Anatomical context of phosphothreonine

• When hepatocytes were grown in the presence of 32PO4, 32P was detected in phosphoserine and phosphothreonine residues of intact L-CAM, but little or no 32P was detected in Ft1, suggesting that L-CAM is phosphorylated in the carboxyl-terminal region [15].
• Phosphorylation of light-harvesting complex II and photosystem II core proteins shows different irradiance-dependent regulation in vivo. Application of phosphothreonine antibodies to analysis of thylakoid phosphoproteins [16].
• The plant plasma membrane H+-ATPase is an unusual target in that a unique phosphothreonine motif (946YpTV, where pT represents phosphothreonine) in the extreme C-terminal end of the H+-ATPase interacts with the binding cleft of 14-3-3 protein (Wurtele, M., Jelich-Ottmann, C., Wittinghofer, A., and Oecking, C. (2003) EMBO J. 22, 987-994) [17].
• The binding of EGF to these membranes in vitro resulted in a severalfold stimulation of the phosphorylation reaction; again, the major phosphorylated amino acid residue detected in partial acid hydrolysates was phosphothreonine [18].
• Treatment of HeLa cells with fetal bovine serum markedly increased the phosphothreonine 410 content of CAT zeta and stimulated its kinase activity [19].

Associations of phosphothreonine with other chemical compounds

• Here, we discover a pocket in the kinase domain of PDK1 that recognizes the phosphoserine/phosphothreonine in the hydrophobic motif by identifying two oppositely positioned arginine and lysine residues that bind the phosphate [20].
• Here we describe the isolation of a high molecular weight ( approximately 440 kDa), cholesterol-regulated pERK phosphatase that dephosphorylates both the phosphotyrosine and the phosphothreonine residues in the activation loop of the enzyme [21].
• The phosphorylation patterns of the normal cell and viral proteins are also similar: both contain two major phosphorylated residues, a phosphoserine located on the NH2-terminal 60% of the polypeptide and a phosphothreonine present on the COOH-terminal 40% of the molecule [22].
• We have found that the epidermal growth factor (EGF) receptor becomes constitutively phosphorylated on tyrosine in cells transformed by the src oncogene and in addition displays elevated levels of phosphoserine and phosphothreonine [23].
• Glutamic acid can substitute for phosphothreonine in some proteins activated by phosphorylation, but this substitution (T169E) at the site of activation loop phosphorylation in the Saccharomyces cerevisiae cyclin-dependent kinase (Cdk) Cdc28p blocks biological function and protein kinase activity [24].

Gene context of phosphothreonine

• MAP kinase phosphatase-3 (MKP-3) dephosphorylates phosphotyrosine and phosphothreonine and inactivates selectively ERK family mitogen-activated protein (MAP) kinases [25].
• PPM1D dephosphorylation of UNG2 at phosphothreonine 6 is associated with reduced UNG2 activity [26].
• Rad53 contains two FHA phosphothreonine-binding domains that are required for Rad53 activation and possibly downstream signaling [27].
• In vitro, Ptc1 but not the metal binding site mutant, Ptc1D58N, inactivated Hog1 by dephosphorylating the phosphothreonine but not the phosphotyrosine residue in the phosphorylation lip [28].
• We find that the three arginines that anchor phosphothreonine 160 of fully active CDK2 do not contribute equally to structural stabilization [29].

Analytical, diagnostic and therapeutic context of phosphothreonine

• Following proteolytic digestion of 32P-labeled pp42/MAP kinase with trypsin, only a single phosphopeptide was detected by two-dimensional peptide mapping, and this peptide contained both phosphotyrosine and phosphothreonine [30].
• The major phosphopeptide (CB-1), containing phosphothreonine as the only radiolabeled amino acid, was purified by reverse-phase high performance liquid chromatography and subjected to automated gas-phase Edman degradation [31].
• Two-dimensional mapping of the radiolabeled phosphopeptides produced from EGF receptors isolated by immunoprecipitation and treated with trypsin revealed 9 independent labeled regions, 2 of which contained phosphothreonine and were present only in EGF- or TPA-treated cells [32].
• The properties of the Mr-22 000 protein include: heat-stability; solubility in 1% trichloroacetic acid; pI 4.9; elution at apparent Mr 37 500 on gel filtration; and it contains both phosphoserine and phosphothreonine [33].
• A simple and rapid procedure is described for fully separating phosphotyrosine from phosphoserine and phosphothreonine through one-dimensional thin-layer chromatography [34].

References