O-Phosphoserine

This should be illustrated by the counterion concentration dependencies of three different model solutes, namely Af-3,5-dinitrobenzoylated serine (DNB-Ser), aspartic acid (DNB-Asp), and O-phosphoserine (DNB-PSer), which are structural analogs that differ in the number of nominal charges. The solutes have been analyzed in the RP mode with methanol-phosphate buffer (50 50 v/v) (pH 6.5) under variable phosphate concentrations. The results are shown in Figure 1.4. 

Photosynthetic phosphorylation of protein side chains 79 substrate level 775, 800 Phosphorylation, photosynthetic. See Photosynthetic phosphorylation Phosphorylation reactions 303 Phosphorylation state ratio definition of 303 O-Phosphoserine 610s Phosphoserine 545 Phosphothreonine 545 Phosphotransferase system bacterial 419,420 Phosphotransferases 637... 

The serine proteases act by forming and hydrolyzing an ester on a serine residue. This was initially established using the nerve gas diisopropyl fluorophosphate, which inactivates serine proteases as well as acetylcholinesterase. It is a very potent inhibitor (it essentially binds in a 1 1 stoichiometry and thus can be used to titrate the active sites) and is extremely toxic in even low amounts. Careful acid or enzymatic hydrolysis (see Section 9.3.6.) of the inactivated enzyme yielded O-phosphoserine, and the serine was identified as residue 195 in the sequence. Chy-motrypsin acts on the compound cinnamoylimidazole, producing an acyl intermediate called cinnamoyl-enzyme which hydrolyzes slowly. This fact was exploited in an active-site titration (see Section 9.2.5.). Cinnamoyl-CT features a spectrum similar to that of the model compound O-cinnamoylserine, on denaturation of the enzyme in urea the spectrum was identical to that of O-acetylserine. Serine proteases act on both esters and amides. 

One approach developed by Isis Innovation Limited (a wholly-owned subsidiary of the University of Oxford) involves the precipitation of calcium phosphate onto collagen at room temperature. When o-phosphoserine is added to the reaction, the calcium phosphate precipitates onto the collagen in the form of small "needles." These structures provide abundant surface area on which osteoblasts and other hone cells can become established. 

Phospholipase C. Using a phospholipase C obtained from Bacillus cere us, the experimental conditions for attack on phosphatidylserine are exactly the same as those described in Chapter 4. The reaction proceeds smoothly and leads to a chloroform-soluble, phosphorus-free product (i.e., diacylglycerol) and a water soluble phosphorus-containing product [i.e., O-phosphoserine (O-PS]). 

Figure 16 Experimental (left) and simulated (middle) low spinning speed (to, = 2.0 kHz) CSA sideband manifolds of phosphate groups in L-O-phosphoserine lyophilised from solutions at different pH values. For better visualisation of the changes in the CSA tensor after secondary ionisation, the corresponding simulated static powder spectra are also included (right).Taken from Ref. [74]. Reproduced by permission of The Royal Society of Chemistry.

Table III. Effect of Temperature on the e Elimination of O-Phosphoserine, O-Glycothreonine and Cystine Groups in Proteins...

Many methanogenic archaeabacteria lack cysteinyl-tRNA synthetase (CysRS). Interestingly, a Class II enzyme called O-phosphoseryl-tRNA synthetase (SepRS) acylates tRNA with O-phosphoserine (Sep) to form Sep-tRNA , which is then converted to Cys-tRNA by the enzyme Sep-tRNA Cys-tRNA synthase (SepCysS). It has been proposed that this indirect pathway may be the sole route for cysteine biosynthesis in these organisms (9). The crystal structure of SepRS was recently... 

Cysteic acid is the major product of performic acid oxidation of cysteine and cystine in proteins, and is usually produced in yields of more than 90%. Cysteic acid is not retarded by the resins generally used in amino acid analyzers and therefore elutes at the breakthrough volume (about 42% of the elution volume of aspartic acid). However, since other substances such as O-phosphoserine can also elute in this position, it is essential to analyze hydrolysates made both before and... 

O-Phosphoserine and 0-phosphothreonine 0-Phosphoserine has been reported in a number of proteins in which it appears to function as an intermediate in enzymic reactions (e.g. phosphoglucomutase), as a regulator of enzymic activity (e.g. phospho-rylase) or protein function (e.g. histones), and as a nutritive component (e.g. casein). O-Phosphothreonine has been reported in some of these proteins, but generally to a much more limited extent and only in those which also contain O-phosphoserine. 

These derivatives are not stable to complete acid hydrolysis of proteins, but may be recovered in limited amounts after partial acid hydrolysis. For example, after 90 min of hydrolysis at 100°C in 5.7 N HCl about 30% of the covalently-bound phosphate in phosphoglucomutase was recovered as O-phosphoserine (Milstein 1964), but after 20 hr of hydrolysis at 105°C in 5.7 N HCl, no O-phosphoserine was found (Murray and Milstein 1967). The amount liberated at a certain time will depend on the nature of the residues around the phosphoserine residues in each protein. Hydrolysis of peptides containing O-phosphoserine may often give low yields of serine (e.g. see Nolan et al. 1964). Complete enzymic hydrolysis of proteins or peptides containing O-phosphoserine is the only presently available method for quantitative recovery of this derivative. 

In most analyzer systems O-phosphoserine and O-phospho-threonine elute at the same volume as cysteic acid (the unretarded position) and can, therefore, interfere with analyses for cysteic acid (and vice versa). The color value for O-phosphoserine is 1.04 times the average value calculated for the amino acids (except proline and cystine) eluted from a 60 cm column in a two-column system (Beckman manuals). It should be noted that O-serine sulfate and O-threonine sulfate, which can be formed during preparation of hydrolysates in the presence of sulfate (Moore 1963 Murray and Milstein 1967), also elute in this position. Electrophoresis at pH 3.5 is an effective means of separating O-phosphoserine from other amino acids, since it migrates... 

PS—polystyrene UF—urea-formaldehyde resin glut—glutaraldehyde thio— thiourea BSA—bovine serum albumin PHEMA—poly(hydroxyethyl methacrylate) IDA—iminodiacetic acid LDH—lactate dehydrogenase OPS—o-phosphoserine 8HQ—8-hydroxyquinoUne Bpa— bis(2-pyridyl-methyl) amine. 

Zacharion, M. Traverso, L Hearn, M.T.W. High-performance liquid chromatography of amino acids, peptides and proteins CXXXI. o-Phosphoserine as a new chelating ligand for use with hard Lewis metal ions in the im-mobilized-metal affinity chromatography of proteins. J. Chromatogr. 1993, 646, 107-120. 

See also O-Phosphoserine, 4-Hydroxyproline,5-Hydroxylysine, Thyroxine,y-Carboxyglutamic acid... 

O-Phosphoserine is a modified form of serine found in proteins as a result of phosphorylation by a protein kinase (an enzyme which puts phosphates onto proteins). 

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