Disease relevance of Isoelectric Point

• Isoelectric focusing indicated that a peak of beta-hexosaminidase activity with an isoelectric point value (9.5) comparable to that of the peak found in increased amounts in malignant colon was detectable in the sera of 36% of the colorectal cancer patients and 11% of the controls [1].
• Further evidence was the coincident isoelectric points of the predominant isoamylase in the sera of the liver disease patients and of patients with parotid inflammatory disease [2].
• Past studies of norepinephrine-stimulated protein phosphorylation in intact C-6 glioma cells had identified a 58,000 molecular weight, 5.7 isoelectric point protein (58K-5.7) as a cyclic AMP-dependent phosphoprotein and had shown that 58K-5.7 was one of the most abundant proteins of the nuclear fraction [3].
• Treatment of adult AcChoR with Escherichia coli alkaline phosphatase decreased its thermal stability and shifted its isoelectric point towards alkaline pH [4].
• Isoelectric focusing profiles for the cytosol fractions from Ehrlich ascites cells and from Novikoff hepatoma cells each consisted essentially of one peak of nucleoside phosphorylase activity [isoelectric points (pl) 5.4 and 5.8, respectively] that cleaved both uridine and thymidine (dThd), as well as FdUrd [5].

Psychiatry related information on Isoelectric Point

• In Alzheimer's disease patients transketolase protein variants with different isoelectric points or a proteolytic cleavage leading to small transketolase protein isoforms have been identified [6].

High impact information on Isoelectric Point

• The antigen can be extracted from cells with isotonic buffers containing EGTA, binds to Concanavalin A, and when analyzed on SDS gels by immunoblotting, two major antigenic glycoproteins are detected at 57 kd (isoelectric point, 5.1) and at 44 kd (isoelectric point, 5.4) [7].
• The prekallikrein activator was identified as Hageman-factor fragments by molecular weight (35,000 as estimated by gel chromatography), isoelectric point (4.2 to 4.4), and inhibition by antibody to Hageman factor [8].
• A temperature-sensitive mutant of the BC complementation group (BC11) of SV40 results in the synthesis of VP1 with an altered electrophoretic mobility; both the major form of VP1 and the minor forms are shifted in their isoelectric points [9].
• This protein turned out to be a N-linked glycoprotein with a 100-kD protein core and isoelectric point 5.8, indicating that it is distinct from CD43 and the BP-1/6C3 antigen [10].
• The Fc alpha R is a heterogenously charged, approximately 60-kD molecule with an isoelectric point of 4.5-5.6 that binds monomeric or polymeric IgA1 and IgA2 molecules [11].

Chemical compound and disease context of Isoelectric Point

• Highly enriched MPIF-alpha and -beta, separated by virtue of their basic isoelectric point and affinity for heparin, induced local induration and fibrin deposition and cellular infiltration similar to that observed in delayed type hypersensitivity reactions, when injected intradermally [12].
• Isoforms (derived from the same isoenzyme but distinguished by differences in isoelectric point) of MM creatine kinase appear in plasma after myocardial infarction [13].
• 30 000-31 000, has a rather low isoelectric point (at pH 6.0) and contains less lysine (2.1%) and more half-cystine residues than most beta-lactamases from other Gram-positive bacteria [14].
• CARB-4, a novel carbenicillin-hydrolyzing beta-lactamase with an isoelectric point of 4.3, was discovered in a strain of Pseudomonas aeruginosa from France. It was determined by a multiresistant transmissible plasmid belonging to the P-2 incompatibility group [15].
• The isoelectric points of polypeptides of standard and dense poliovirus particles and of empty capsids have been determined by isoelectric focusing in urea and by two-dimensional analysis [16].

Biological context of Isoelectric Point

• Transfection of the mutant cDNA into heterologous cells resulted in expression of a heat-labile ADA of normal electrophoretic mobility and isoelectric point, properties exhibited by the ADA in the patients' cells [17].
• Here we identified this protein as the 70-kD heat shock cognate protein (hsc70) based on its mass, isoelectric point, cellular localization, and partial amino acid sequences [18].
• The fact that the Na+ site and glucose site probes bind to a 75-kDa polypeptide, copurify with the same isoelectric point (pI 5.3) and retain function, and exhibit energy transfer indicates that the sites are on the same 75-kDa polypeptide [19].
• An isoenzyme of the catalytic subunit of type II cyclic AMP-dependent protein kinase from rat muscle is reported which coelutes with the classical catalytic subunit but differs from it in isoelectric point (pI 8.7 vs pI 9.1) and is enzymmatically inactive [20].
• The correlation between a basic shift in isoelectric point in Drosophila GDI in quartet mutant tissue and the quartet developmental phenotype raises the possibility that a posttranslational modification of GDI is necessary for its function and that GDI function is essential for development [21].

Anatomical context of Isoelectric Point

• Eosinophil granule major basic protein (MBP), a potent toxin for helminths and various cell types, is a 13.8-kD single polypeptide rich in arginine with a calculated isoelectric point (pI) of 10 [22].
• Creatine kinase (CK, EC 2.7.3.2) has recently been identified as the intermediate isoelectric point species (pl 6.5-6.8) of the Mr 40,000-43,000 nonreceptor, peripheral v-proteins in Torpedo marmorata acetylcholine receptor-rich membranes (Barrantes, F. J., G. Mieskes, and T. Wallimann, 1983, Proc. Natl. Acad. Sci. USA, 80: 5440-5444) [23].
• The isoelectric points of tubulin from both unfertilized oocytes and isolated meiotic spindles were 5.8 for alpha tubulin and 5.6 for beta tubulin [24].
• Highly purified platelet glucose-6-phosphate dehydrogenase (G6PD; D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49) can be modified in its isoelectric point and its molecular specific activity by extracts of some leukemic granulocytes [25].
• The apparent molecular weights, isoelectric points, and antigenic properties of EGF-alpha and EGF-beta were identical, and both forms stimulated a mitogenic response in 3T3 cells [26].

Associations of Isoelectric Point with chemical compounds

• Two-dimensional polyacrylamide gel electrophoresis revealed that the 90,000-Mr peptide found on BFT was an acidic protein of isoelectric point (pI) 5.0, whereas, the 75,000-Mr peptide form culture-form trypomastigotes has a pI of 7 [27].
• J774 FcR was judged to be a glycoprotein based on the sensitivity of its isoelectric point to neuraminidase digestion, its labeling with galactose oxidase/NaB[3H4], and its binding to concanavalin A-Sepharose [28].
• The S region of H-2 controls a polymorphism of the gamma-chain of C4 (gamma 1, gamma 2, and gamma 3) as shown by differences in their isoelectric points [29].
• The native protein had an isoelectric point of 3.5, stained with periodic acid-Schiff but not Sudan black, and contained 4 mol of sialic acid per mol of protein [30].
• All three variant proteins are indistinguishable from IXN in their amino acid compositions, isoelectric points, carbohydrate distributions and number of gamma-carboxyglutamic acid residues [31].

Gene context of Isoelectric Point

• Although cachectin's isoelectric point and molecular weight are similar to those described for interleukin 1, pure cachectin has no leukocyte-activating factor (LAF) activity [32].
• Although the primary sequence relatedness to kinesin is weak in the remainder of the molecule, the predicted secondary structure and regional isoelectric points are similar to kinesin heavy chain [33].
• The normal allele directed synthesis of immunoreactive ALDH2 protein (ALDH2E) with the expected isoelectric point [34].
• When human kidney hexosaminidase A was dissociated into its subunits by p-hydroxymercuribenzoate, three distinct proteins having isoelectric points of pH 7.2.5.4, and 4.3 were isolated [35].
• The fraction having an isoelectric point of pH 7.2, designated as beta fraction, was electrophoretically and immunologically identical to hexosaminidase B and was enzymatically active [35].

Analytical, diagnostic and therapeutic context of Isoelectric Point

• Analysis of 20K neurophysin in cell extract by isoelectric focusing on polyacrylamide gel demonstrated that it was principally composed of a protein with an apparent isoelectric point (pI) of 5 [36].
• A variant of apo C-II (apo C-IIPadova) with lower apparent molecular weight and more acidic isoelectric point was identified in both probands by two-dimensional gel electrophoresis [37].
• As determined by the molecular mass and isoelectric point on 2-dimensional gels and Western immunoblot with a specific 90 kDa heat shock protein (HSP90) monoclonal antibody, the unknown protein was identified as HSP90 [38].
• Six basic proteins of 26 to 38 kDa with isoelectric points (pI) > or = 8.5 were abundant in proteins separated by two-dimensional SDS-PAGE from adult rat peritoneal mast cells (MC) [39].
• The purified complex migrated as a single peak with an apparent sedimentation coefficient of approximately 30 and approximately 9 S upon density gradient centrifugation and with isoelectric points of 3.7 and 3.9 upon two-dimensional gel electrophoresis in Chaps and Zwittergent 3-14, respectively [40].

References