Detection of histidine kinases via a filter-based assay and reverse-phase thin-layer chromatographic phosphoamino acid analysis

The methods that detect histidine phosphorylation have largely been either laborious or difficult to apply quantitatively. The major difficulty in assessing for its presence is its alkali-stable, acid-labile nature. While an assay that detects alkali-stable phosphorylation has been developed, it does not distinguish phosphohistidine from other alkali-stable phosphoamino acids. Using this established method, we extend the assay to facilitate the specific detection of phosphohistidine. We use the acid-lability of phosphohistidine as a defining feature in our approach for its detection. In addition, reverse-phase thin-layer chromatography was utilized to conclusively demonstrate the viability of the conditions that we implement in the assay for the selective detection of phosphohistidine. In summary, this report describes a rapid filter-based kinase assay that quantitatively measures histidine kinase activity, even in the presence of tyrosine kinase activity.     

磷酸化组氨酸研究进展

蛋白质磷酸化是生物体内一种广泛存在的蛋白质翻译后修饰形式,这种氨基酸与磷酸基团共价连接的修饰模式对蛋白质结构和功能起到了重要调节作用.目前天然蛋白质中发现的可磷酸化位点主要有9种氨基酸残基,其中包括以磷酰胺连接的磷酸化组氨酸.虽然该磷酸化形式在原核生物与真核生物中都起到了重要的调节作用,但对于其生物学功能的研究长期存在技术困难.由于磷酸化组氨酸本身不同于其他磷酸化氨基酸的化学性质,如存在异构体、化学不稳定等,其在传统的研究方法中容易发生水解去磷酸化.随着现代生物化学与分子生物学技术的不断进步,人们针对含有磷酸化组氨酸的蛋白质构建了新的制备、分离与表征策略,本领域也因此开始迅速发展.本文从磷酸化组氨酸的化学结构入手,分析其两种异构体的主要理化性质与化学反应特性,并概述了基于此发展的新型化学生物学研究手段以及对于磷酸化组氨酸生物功能的研究进展.     

Identification and characterization of a mammalian 14-kDa phosphohistidine phosphatase.

Protein histidine phosphorylation in eukaryotes has been sparsely studied compared to protein serine/threonine and tyrosine phosphorylation. In an attempt to rectify this by probing porcine liver cytosol with the phosphohistidine-containing peptide succinyl-Ala-His(P)-Pro-Phe-p-nitroanilide (phosphopeptide I), we observed a phosphatase activity that was insensitive towards okadaic acid and EDTA. This suggested the existence of a phosphohistidine phosphatase different from protein phosphatase 1, 2A and 2C. A 1000-fold purification to apparent homogeneity gave a 14-kDa phosphatase with a specific activity of 3 micro mol.min-1.mg-1 at pH 7.5 with 7 micro m phosphopeptide I as substrate. Partial amino-acid sequence determination of the purified porcine enzyme by MS revealed similarity with a human sequence representing a human chromosome 9 gene of hitherto unknown function. Molecular cloning from a human embryonic kidney cell cDNA-library followed by expression and purification, yielded a protein with a molecular mass of 13 700 Da, and an EDTA-insensitive phosphohistidine phosphatase activity of 9 micro mol.min-1.mg-1 towards phosphopeptide I. No detectable activity was obtained towards a set of phosphoserine-, phosphothreonine-, and phosphotyrosine peptides. Northern blot analysis indicated that the human phosphohistidine phosphatase mRNA was present preferentially in heart and skeletal muscle. These results provide a new tool for studying eukaryotic histidine phosphorylation/dephosphorylation.     

Mutational study of human phosphohistidine phosphatase: effect on enzymatic activity

Although protein histidine phosphorylation is estimated to account for about 6% of total protein phosphorylation in eukaryotes, knowledge on histidine phosphorylation and dephosphorylation is still limited. Recently, a few reports have appeared on a mammalian 14-kDa phosphohistidine phosphatase, also named protein histidine phosphatase. Molecular cloning of the protein has opened possibilities for exploring its properties and physiological role. In the present work, we have searched for potential active site residues in the human phosphohistidine phosphatase by point mutations of conserved histidine and arginine residues to alanine. When assayed by the phosphohistidine-containing peptide succinyl-Ala-His(P)-Pro-Phe-p-nitroanilide, mutants H53A and H102A showed no detectable activity. Compared to the wild-type recombinant enzyme, the specific activity of mutant R45A was decreased by one order of magnitude, that of mutant R78A was decreased by about 30%, while that of mutant H81A was essentially unchanged. These results will facilitate future studies of the reaction mechanism, substrate binding, and molecular structure of the phosphohistidine phosphatase.     

Mass spectrometric analysis of protein histidine phosphorylation

Summary. Protein histidine phosphorylation is now recognized as an important form of post-translational modification. The acid-lability of phosphohistidine has meant that this phosphorylation has not been as well studied as serine/threonine or tyrosine phosphorylation. We show that phosphohistidine and phosphohistidine-containing phosphopeptides derived from proteolytic digestion of phosphohistone H4 are detectable by ESI-MS. We also demonstrate reverse-phase HPLC separation of these phosphopeptides and their detection by MALDI-TOF-MS.     

Protein histidine phosphorylation: increased stability of thiophosphohistidine.

Posttranslational phosphorylation of proteins is an important event in many cellular processes. Whereas phosphoesters of serine, threonine and tyrosine have been extensively studied, only limited information is available for other amino acids modified by a phosphate group. The formation of phosphohistidine residues in proteins has been discovered in prokaryotic organisms as well as in eukaryotic cells. The ability to biochemically analyze phosphohistidine residues in proteins, however, is severely hampered by its extreme lability under acidic conditions. In our studies we have found that by replacing the phosphate linked to the histidine residue with a thiophosphate, a phosphohistidine derivative with increased stability is formed. This allows the analysis of phosphohistidine-containing proteins by established biochemical techniques and will greatly aid in the investigation of the role of this posttranslational modification in cellular processes.     

A filter-based protein kinase assay selective for alkali-stable protein phosphorylation and suitable for acid-labile protein phosphorylation

Alkali-stable phosphorylation of proteins, particularly phosphotyrosine and phosphohistidine, is an important phenomenon in cells. In the case of phosphohistidine and some other phosphoamino acids, the phosphorylation is acid-labile and in these cases studies have been severely limited by the absence of a rapid assay suitable for acid-labile phosphorylation. The assay presented here involves a conventional kinase assay reaction followed by mild alkaline hydrolysis and adsorption of the product to washed Nytran paper at high pH. After further washing, at pH 9, the radioactivity on the papers is determined by liquid scintillation counting. Hence, acid-labile phosphorylation is preserved. The assay is selective for alkali-stable phosphorylation but not fully specific, mainly due to the need to balance the severity of the partial alkaline hydrolysis with the stability of the protein-peptide bonds. The assay has been used for the purification and characterization of a protein histidine kinase from Saccharomyces cerevisiae.     

蛋白组氨酸磷酸酶研究进展

主要概括磷酸酶的种类,原核细胞磷酸组氨酸生物功能及调控,哺乳动物组氨酸残基磷酸化、去磷酸化,以及组氨酸磷酸酶及其底物的最新研究进展. 信号转导在生长发育及细胞功能中起极其重要的作用. 无论在原核还是真核细胞,蛋白质磷酸化是细胞内信号转导的关键机制. 研究最多的可逆的真核蛋白磷酸化,主要发生在含有羟基的丝氨酸、苏氨酸和酪氨酸残基上. 不同的激酶和磷酸酶受不同机制的调节,而调节过程中出现的差异是人类很多疾病的潜在基础. 与大量有关羟基磷酸化氨基酸的报道相比,有关氨基磷酸化氨基酸的报道甚少. 据估计,自然界中存在的磷酸组氨酸比磷酸酪氨酸多10 ~ 100倍,但不如磷酸丝氨酸丰富. 虽然对脊椎动物蛋白质中存在磷酸组氨酸的认识可以追溯到20世纪60年代初, 但由于研究手段的限制,至今对脊椎动物蛋白组氨酸激酶及组氨酸磷酸酶的结构及功能知之甚少. 但是,近几年的研究有突破性的发现,克隆和重组表达哺乳动物组氨酸磷酸酶为研究氨基磷酸化氨基酸的生物功能翻开新的一章.     

Focus on phosphohistidine

Summary. Phosphohistidine has been identified as an enzymic intermediate in numerous biochemical reactions and plays a functional role in many regulatory pathways. Unlike the phosphoester bond of its cousins (phosphoserine, phosphothreonine and phosphotyrosine), the phosphoramidate (P–N) bond of phosphohistidine has a high ΔG° of hydrolysis and is unstable under acidic conditions. This acid-lability has meant that the study of protein histidine phosphorylation and the associated protein kinases has been slower to progress than other protein phosphorylation studies. Histidine phosphorylation is a crucial component of cell signalling in prokaryotes and lower eukaryotes. It is also now becoming widely reported in mammalian signalling pathways and implicated in certain human disease states. This review covers the chemistry of phosphohistidine in terms of its isomeric forms and chemical derivatives, how they can be synthesized, purified, identified and the relative stabilities of each of these forms. Furthermore, we highlight how this chemistry relates to the role of phosphohistidine in its various biological functions.     

Mammalian protein histidine kinases

The existence of protein kinases, known as histidine kinases, which phosphorylate their substrates on histidine residues has been well documented in bacteria and also in lower eukaryotes such as yeast and plants. Their biological roles in cellular signalling pathways within these organisms have also been well characterised. The evidence for the existence of such enzymes in mammalian cells is much less well established and little has been determined about their cellular functions. The aim of the current review is to present a summary of what is known about mammalian histidine kinases. In addition, by consideration of the chemistry of phosphohistidine, what is currently known of some mammalian histidine kinases and the way in which they act in bacteria and other eukaryotes, a general role for mammalian histidine kinases is proposed. A histidine kinase phosphorylates a substrate protein, by virtue of the relatively high free energy of hydrolysis of phosphohistidine the phosphate group is easily transferred to either a small molecule or another protein with which the phosphorylated substrate protein specifically interacts. This allows a signalling process to occur, which may be downregulated by the action of phosphatases. Given the known importance of protein phosphorylation to the regulation of almost all aspects of cellular function, the investigation of the largely unexplored area of histidine phosphorylation in mammalian cells is likely to provide a greater understanding of cellular action and possibly provide a new set of therapeutic drug targets.     

蛋白质组氨酸磷酸化研究进展

摘要：蛋白质磷酸化是一种可逆的翻译后修饰,这种翻译后修饰可以改变蛋白质的构象,进而使蛋白质活化或者失活。组氨酸磷酸化在细胞信号传导过程中发挥着重要作用,且组氨酸磷酸化与人类某些疾病密切相关,然而,由于组氨酸磷酸化含有P-N键,具备不稳定性,有关于组氨酸磷酸化的报道远远少于其它磷酸化的报道。本综述系统的总结了组氨酸磷酸化在生物学过程中的作用,以及近些年取得的重要研究进展,以期对深入研究组氨酸磷酸化提供理论参考。     

Histidine phosphorylation in biological systems

Histidine phosphorylation is important in prokaryotes and occurs to the extent of 6% of total phosphorylation in eukaryotes. Nevertheless phosphohistidine residues are not normally observed in proteins due to rapid hydrolysis of the phosphoryl group under acidic conditions. Many rapid processes employ phosphohistidines, including the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS), the bacterial two-component systems and reactions catalyzed by enzymes such as nucleoside diphosphate kinase and succinyl-CoA synthetase. In the PTS, the NMR structure of the phosphohistidine moiety of the phosphohistidine-containing protein was determined but no X-ray structures of phosphohistidine forms of PTS proteins have been elucidated. There have been crystal structures of a few phosphohistidine-containing proteins determined: nucleoside diphosphate kinase, succinyl-CoA synthetase, a cofactor-dependent phosphoglycerate mutase and the protein PAE2307 from the hyperthermophilic archaeon Pyrobaculum aerophilum. A common theme for these stable phosphohistidines is the occurrence of ion-pair hydrogen bonds (salt bridges) involving the non-phosphorylated nitrogen atom of the histidine imidazole ring with an acidic amino acid side chain.     

Chemical phosphorylation of histidine-containing peptides based on the sequence of histone H4 and their dephosphorylation by protein histidine phosphatase

Using peptides based on the amino acid sequences surrounding the two histidine residues in histone H4, we have investigated the kinetics of the phosphorylation and dephosphorylation reactions of their histidine residues, when reacted with potassium phosphoramidate, by ¹H NMR. We have been able to estimate rate constants for the reactions and have shown that there are differences in the kinetics between the two peptides. The kinetics of hydrolysis of phosphoramidate was measured by ³¹P NMR and protein histidine phosphatase (PHP) was shown to catalyse the reaction. We have shown that the dephosphorylation of the phosphohistidine of the phosphopeptides is catalysed by PHP. In terms of substrate specificity, there is a small preference for 1-phosphohistidine compared to 3-phosphohistidine, although the rate accelerations for hydrolysis induced by the enzyme were 1100- and 33,333-fold, respectively. The kinetics of both the phosphorylation and dephosphorylation reactions depend on the amino acid sequence surrounding the histidine. PHP shows greater substrate specificity for the peptide whose sequence is similar to that around histidine 18 of histone H4. PHP was unable to catalyse the dephosphorylation of histone H4 that had been phosphorylated with a histone H4 histidine kinase.     

Phosphorylation and dephosphorylation of histidine residues in proteins.

Protein phosphorylation is a key mechanism for intracellular signal transduction in both prokaryotic and eukaryotic cells. Vertebrate proteins are prevalently phosphorylated on side chains that contain a hydroxyl group, such as serine, threonine and tyrosine residues. In the past decade, however, an increasing number of examples of histidine phosphorylation has been described. Because acid treatment of phosphoproteins during purification and detection of phosphoamino acid analysis is routine, O-phosphomonoesters have been studied more often, and the existence of acid-labile phosphates has been largely overlooked. The latter class of N-phosphoamidates may well be more widespread than is generally believed, even though the O-phosphates remain the major class in terms of quantity and extent of distribution in proteins. Phosphohistidine currently is estimated to be 10- to 100-fold more abundant than phosphotyrosine, but less abundant than phosphoserine [Matthews, H.R. (1995) Pharmac. Ther. 67, 323-350.]. This minireview briefly summarizes the extensive knowledge of the key mechanisms and functions of phosphohistidine in bacteria. It also describes the still limited, yet increasing, data from homologs of the bacterial two-component system. Finally, novel mechanisms of phosphorylation and dephosphorylation of histidine residues not related to the two-component system are described.     

组氨酸磷酸化修饰的鉴定方法及应用

蛋白质磷酸化是广受关注的翻译后修饰类型之一,组氨酸磷酸化作为一种非常见的磷酸化修饰,最早被发现在细菌和低等真核生物信号传导的级联反应中起关键作用.近年来研究显示,其在肿瘤发生发展过程中也可能扮演了重要角色.由于磷酸化组氨酸的化学不稳定性、低丰度、亚化学计量性质、缺乏特异性的富集试剂,导致研究手段缺乏,限制了人们对磷酸化...     

High resolution structure of the phosphohistidine-activated form of Escherichia coli cofactor-dependent phosphoglycerate mutase

The active conformation of the dimeric cofactor-dependent phosphoglycerate mutase (dPGM) from Escherichia coli has been elucidated by crystallographic methods to a resolution of 1.25 A (R-factor 0.121; R-free 0.168). The active site residue His(10), central in the catalytic mechanism of dPGM, is present as a phosphohistidine with occupancy of 0.28. The structural changes on histidine phosphorylation highlight various features that are significant in the catalytic mechanism. The C-terminal 10-residue tail, which is not observed in previous dPGM structures, is well ordered and interacts with residues implicated in substrate binding; the displacement of a loop adjacent to the active histidine brings previously overlooked residues into positions where they may directly influence catalysis. E. coli dPGM, like the mammalian dPGMs, is a dimer, whereas previous structural work has concentrated on monomeric and tetrameric yeast forms. We can now analyze the sequence differences that cause this variation of quaternary structure.     

Purification of a serine and histidine phosphorylated mitochondrial nucleoside diphosphate kinase from Pisum sativum.

For the first time, to our knowledge, a nucleoside diphosphate kinase (NDPK) has been purified from plant mitochondria (Pisum sativum L.). In intact pea leaf mitochondria, a 17.4-kDa soluble protein was phosphorylated in the presence of EDTA when [gamma-32P]ATP was used as the phosphate donor. Cell fractionation demonstrated that the 17.4-kDa protein is a true mitochondrial protein, and the lack of accessibility to EDTA of the matrix compartment in intact mitochondria suggested it may have an intermembrane space localization. The 17.4-kDa protein was purified from mitochondrial soluble proteins using ATP-agarose and anion exchange chromatography. Amino-acid sequencing of two peptides, resulting from a trypsin digestion, revealed high similarity with the conserved catalytic phosphohistidine site and with the C-terminal of NDPKs. Acid and alkali treatments of [32P]-labelled pea mitochondrial NDPK indicated the presence of acid-stable as well as alkali-stable phosphogroups. Thin-layer chromatography experiments revealed serine as the acid-stable phosphogroup. The alkali-stable labelling probably reflects phosphorylation of the conserved catalytic histidine residue. In phosphorylation experiments, the purified pea mitochondrial NDPK was labelled more heavily on serine than histidine residues. Furthermore, kinetic studies showed a faster phosphorylation rate for serine compared to histidine. Both ATP and GTP could be used as phosphate donor for histidine as well as serine labelling of the pea mitochondrial NDPK.     

Histidine phosphorylation of annexin I in airway epithelia

Although [Cl(-)](i) regulates many cellular functions including cell secretion, the mechanisms governing these actions are not known. We have previously shown that the apical membrane of airway epithelium contains a 37-kDa phosphoprotein (p37) whose phosphorylation is regulated by chloride concentration. Using metal affinity (chelating Fe(3+)-Sepharose) and anion exchange (POROS HQ 20) chromatography, we have purified p37 from ovine tracheal epithelia to electrophoretic homogeneity. Sequence analysis and immunoprecipitation using monoclonal and specific polyclonal antibodies identified p37 as annexin I, a member of a family of Ca(2+)-dependent phospholipid-binding proteins. Phosphate on [(32)P]annexin I, phosphorylated using both [gamma-(32)P]ATP and [gamma-(32)P]GTP, was labile under acidic but not alkaline conditions. Phosphoamino acid analysis showed the presence of phosphohistidine. The site of phosphorylation was localized to a carboxyl-terminal fragment of annexin I. Our data suggest that cAMP and AMP (but not cGMP) may regulate annexin I histidine phosphorylation. We propose a role for annexin I in an intracellular signaling system involving histidine phosphorylation.     

Mammalian histidine kinases

Protein phosphorylation is one of the most ubiquitous and important types of post-translational modification for the regulation of cell function. The importance of two-component histidine kinases in bacteria, fungi and plants has long been recognised. In mammals, the regulatory roles of serine/threonine and tyrosine kinases have attracted most attention. However, the existence of histidine kinases in mammalian cells has been known for many years, although little is still understood about their biological roles by comparison with the hydroxyamino acid kinases. In addition, with the exception of NDP kinase, other mammalian histidine kinases remain to be identified and characterised. NDP kinase is a multifunctional enzyme that appears to act as a protein histidine kinase and as such, to regulate the activation of some G-proteins. Histone H4 histidine kinase activity has been shown to correlate with cellular proliferation and there is evidence that it is an oncodevelopmental marker in liver. This review mainly concentrates on describing recent research on these two types of histidine kinase. Developments in methods for the detection and assay of histidine kinases, including mass spectrometric methods for the detection of phosphohistidines in proteins and in-gel kinase assays for histone H4 histidine kinases, are described. Little is known about inhibitors of mammalian histidine kinases, although there is much interest in two-component histidine kinase inhibitors as potential antibiotics. The inhibition of a histone H4 histidine kinase by genistein is described and that of two-component histidine kinase inhibitors of structurally-related mammalian protein kinases. In addition, recent findings concerning mammalian protein histidine phosphatases are briefly described.