双向电泳分析鸢尾绿白嵌合叶片的蛋白质

利用双向聚丙烯酰胺凝胶电泳对鸢尾（Iris japonica)绿白嵌合叶片的蛋白质进行分离,并初步鉴定了蛋白质的相对分子量和等电点。每个电泳图谱共检测到400余个蛋白点,其中至少13个蛋白的表达变化明显;结果表明,嵌合叶片的绿色与白色叶组织具有明显不同的蛋白质双向电泳图谱。与数据库中拟南芥双向电泳图谱相比较,发现Rubisco大亚基,标记为W和T蛋白的表达变化与产生绿白嵌合叶片的表型密切相关。     

Analysis of the cytosolic proteome of Halobacterium salinarum and its implication for genome annotation

The halophilic archaeon Halobacterium salinarum (strain R1, DSM 671) contains 2784 protein-coding genes as derived from the genome sequence. The cytosolic proteome containing 2042 proteins was separated by two-dimensional gel electrophoresis (2-DE) and systematically analyzed by a semi-automatic procedure. A reference map was established taking into account the narrow isoelectric point (pI) distribution of halophilic proteins between 3.5 and 5.5. Proteins were separated on overlapping gels covering the essential areas of pI and molecular weight. Every silver-stained spot was analyzed resulting in 661 identified proteins out of about 1800 different protein spots using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) peptide mass fingerprinting (PMF). There were 94 proteins that were found in multiple spots, indicating post-translational modification. An additional 141 soluble proteins were identified on 2-D gels not corresponding to the reference map. Thus about 40% of the cytosolic proteome was identified. In addition to the 2784 protein-coding genes, the H. salinarum genome contains more than 6000 spurious open reading frames longer than 100 codons. Proteomic information permitted an improvement in genome annotation by validating and correcting gene assignments. The correlation between theoretical pI and gel position is exceedingly good and was used as a tool to improve start codon assignments. The fraction of identified chromosomal proteins was much higher than that of those encoded on the plasmids. In combination with analysis of the GC content this observation permitted an unambiguous identification of an episomal insert of 60 kbp ("AT-rich island") in the chromosome, as well as a 70 kbp region from the chromosome that has integrated into one of the megaplasmids and carries a series of essential genes. About 63% of the chromosomally encoded proteins larger than 25 kDa were identified, proving the efficacy of 2-DE MALDI-TOF MS PMF technology. The analysis of the integral membrane proteome by tandem mass spectrometric techniques added another 141 identified proteins not identified by the 2-DE approach (see following paper).     

Detection of protein-protein interactions and a group of immunoglobulin G-associated minor proteins in human plasma by nondenaturing and denaturing two-dimensional gel electrophoresis

The dissociation of noncovalently associated protein-protein complexes in human plasma was examined by comparing two-dimensional gel electrophoresis (2-DE) patterns obtained in two different electrophoretic conditions. A type I 2-DE pattern was obtained running nondenaturing isoelectric focusing (IEF) followed by nondenaturing gel electrophoresis and a type II 2-DE pattern was nondenaturing IEF followed by sodium dodecyl sulfate gel electrophoresis. Micro-sized gels (internal diameter(id) 1.3 x 35 mm polyacrylamide IEF gels and 38 x 38 x 1 mm polyacryamide slab gels) were used to follow the dissociation processes of major plasma proteins. Larger gel sizes (id 3.4 x 160 mm agarose IEF gels and 160 x 120 x 2.8 mm polyacrylamide slab gels) were used to detect minor plasma proteins dissociated from major proteins. About 110 spots, which have not been detected on type I (nondenaturing) 2-D gels, newly appeared on type II large-sized 2-D gels at molecular masses smaller than 67 kDa. Some of these spots had been analyzed and identified, but about 70 minor spots (isoelectric point 5.5-7.5 and relative molecular mass 8-45 kDa) were detected for the first time by applying large volumes of human plasma samples to the large type II 2-D gels. These minor spots could be concentrated on type II 2-D gels by enriching the immunoglobulin G (IgG) fraction under nondenaturing conditions, and they disappeared when IgG was removed from the fraction. These results strongly suggest that many of the minor spots newly detected were bound to IgG in physiological conditions.     

Effectiveness and limitation of two-dimensional gel electrophoresis in bacterial membrane protein proteomics and perspectives

Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) using isoelectric focusing and SDS-PAGE in the first and second dimensions, respectively, is an established means of simultaneously separating over 1000 proteins and two new types have recently been developed. These procedures have significant shortcomings such as low load ability and poor separation of hydrophobic, acidic and alkaline proteins. We therefore modified the protocols to analyze the Bacillus subtilis membrane proteome. The 2D-PAGE techniques effectively separated membrane proteins having one and two transmembrane segments but not those with more than four. Compared with new LC/MS/MS procedures that are independent of electrophoretic separation, 2D-PAGE can globally analyze and quantify proteins at various stages of the cell cycle when labeled with isotopes such as 35S-methionine or the stable isotope, 15N.     

Separation of human erythrocyte membrane associated proteins with one-dimensional and two-dimensional gel electrophoresis followed by identification with matrix-assisted laser desorption/ionization-time of flight mass spectrometry

A classical proteomic analysis was used to establish a reference map of proteins associated with healthy human erythrocyte ghosts. Following osmotic lysis and differential centrifugation, ghost proteins were separated by either one-dimensional gel electrophoresis (1-DE) or two-dimensional gel electrophoresis (2-DE). Selected protein bands or spots were excised and trypsinized before mass spectrometric analyses and data mining was performed using the SWISS-PROT and NCBI nonredundant databases. A total of 102 protein spots from a 2-D gel were successfully identified. These corresponded to 59 distinct polypeptides with the remaining 43 being isoforms. As for the 1-D gel, 44 polypeptides were identified, of which 19 were also found on the 2-D gel. Most of the 19 common polypeptides were membrane cytoskeletal proteins that are often referred to as the "band" proteins. The remaining 25 polypeptides that were found exclusively on 1-D gels were proteins with high hydrophobicity (e.g., sorbitol dehydrogenase and glucose transporter) and high molecular mass (e.g., Kell blood group glycoprotein and Janus-kinase 2). A higher number of signaling proteins was also identified on 1-D gels compared to 2-D gels. These included Ras, cAMP dependent protein kinase and TGF-beta receptor type 1 precursor.     

Subunit C of the vacuolar H+-ATPase of Hordeum vulgare.

The molecular cloning of the first subunit C of the plant vacuolar H+-ATPase is reported. Tonoplast vesicles were purified from barley leaves by sucrose gradient centrifugation, and the tonoplast polypeptides were separated by two-dimensional (2-D) gel electrophoresis. Using an anti-ATPase holoenzyme antibody, a polypeptide was recognized in the molecular mass range of 40 kDa with an isoelectric point of about 6.0, and tentatively identified as subunit C. The polypeptide spot was excised from about 50 2-D gels and subjected to endo Lys C proteolysis. Two proteolytic peptides were sequenced and the amino acid sequences were used to design degenerated oligonucleotides, followed by PCR amplification with cDNA template and screening of a cDNA library synthesized from Hordeum vulgare poly A mRNA of epidermis strips. The full length clone of 1.5 kbp contains an open reading frame of 1062 bp encoding a polypeptide of 354 amino acids with a molecular mass of 39,982 Da and an isoelectric point of 6.04. Amino acid identity with sequences of SUC from animals and fungi is in the range of 36.7 to 38.5%. Expression of the cloned gene was demonstrated by Northern blotting and RT-PCR.     

Initial proteome analysis of mature barley seeds and malt

Several barley (Hordeum vulgare) cultivars are used in the production of malt for brewing. The malt quality depends on the cultivar, its growth and storage conditions, and the industrial process. To enhance studies on malt quality, we embarked on a proteome analysis approach for barley seeds and malt. The proteome analysis includes two-dimensional (2-D) gel electrophoresis, mass spectrometry, and bioinformatics for identification of selected proteins. This project initially focused on proteins in major spots in the neutral isoelectric point range (pI 4-7) including selected spots that differ between four barley cultivars. The excellent malting barley cultivar Barke was used as reference. Cultivar differences in the 2-D gel spot patterns are observed both at the seed and the malt level. In seed extracts one of the proteins causing variations has been identified as an alpha-amylase/trypsin inhibitor. In malt extracts multiple forms of the alpha-amylase isozyme 2 have been identified in varying cultivar characteristic spot patterns. The present identification of proteins in major spots from 2-D gels includes 27 different proteins from 42 spots from mature seed extract, while only three specific proteins were identified by analysing 13 different spots from the corresponding malt extract. It is suggested that post-translational processing causes the same protein to occur in different spots.     

A reference map of a human pituitary adenoma proteome

In order to compare the proteomes from different cell types of pituitary adenomas for our long-term goal to clarify the molecular mechanisms that participate in the formation of pituitary adenoma, and to detect any tumor-related marker for an "early-stage" diagnosis, the two-dimensional gel electrophoresis (2-DE) reference map of a pituitary adenoma tissue proteome is described here. A vertical, two-dimensional (2-D) polyacrylamide gel electrophoresis system and PDQuest image analysis software have been used to provide a high level of between-gel reproducibility and to accurately array each protein expressed in a pituitary adenoma tissue. Mass spectrometry (matrix-assisted laser desorption/ionization-time of flight MALDI-TOF and liquid chromatography-electrospray ionization-quadrupole-ion trap LC-ESI-Q-IT) and protein databases were used to characterize each protein in the 2-D gel. The results demonstrate that a good reproducibility of the 2-D gel pattern was attained. The position deviation of matched spots among four 2-D gels was 1.95 +/- 0.45 mm in the isoelectric focusing direction, and 1.70 +/- 0.53 mm in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis direction. A total of ca. 1000 protein spots were separated by 2-DE, and 135 protein spots that represent 111 proteins were characterized with mass spectrometry (96 spots for MALDI-TOF, 39 spots for LC-ESI-Q-IT). The characterized proteins include pituitary hormones, cellular signals, enzymes, cellular-defense proteins, cell-structure proteins, transport proteins, etc. Those proteins were located in the cytoplasmic, cellular membrane, mitochondrial, endoplasmic reticulum, nuclear, ribonucleosome, extracellular fractions, or were secreted in plasma, etc. Those identified proteins contribute to a functional profile of the pituitary adenoma proteome. These data will be used to expand the proteome database of the human pituitary, which can be accessed in the website http://www.utmem.edu /proteomics.     

Comparative proteome analysis of Chlamydia trachomatis serovar A, D and L2

Chlamydia trachomatis represents a group of human pathogenic obligate intracellular and gram-negative bacteria. The genome of C. trachomatis D comprises 894 open reading frames (ORFs). In this study the global expression of genes in C. trachomatis A, D and L2, which are responsible for different chlamydial diseases, was investigated using a proteomics approach. Based on silver stained two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), gels with purified elementary bodies (EB) and auto-radiography of gels with 35S-labeled C. trachomatis proteins up to 700 protein spots were detectable within the range of the immobilized pH gradient (IPG) system used. Using mass spectrometry and N-terminal sequencing followed by database searching we identified 250 C. trachomatis proteins from purified EB of which 144 were derived from different genes representing 16% of the ORFs predicted from the C. trachomatis D genome and the 7.5 kb C. trachomatis plasmid. Important findings include identification of proteins from the type III secretion apparatus, enzymes from the central metabolism and confirmation of expression of 25 hypothetical ORFs and five polymorphic membrane proteins. Comparison of serovars generated novel data on genetic variability as indicated by electrophoretic variation and potentially important examples of serovar specific differences in protein abundance. The availability of the complete genome made it feasible to map and to identify proteins of C. trachomatis on a large scale and the integration of our data in a 2-D PAGE database will create a basis for post genomic research, important for the understanding of chlamydial development and pathogenesis.     

Total Protein Extraction and 2-D Gel Electrophoresis Methods for Burkholderia Species

The investigation of the intracellular protein levels of bacterial species is of importance to understanding the pathogenic mechanisms of diseases caused by these organisms. Here we describe a procedure for protein extraction from Burkholderia species based on mechanical lysis using glass beads in the presence of ethylenediamine tetraacetic acid and phenylmethylsulfonyl fluoride in phosphate buffered saline. This method can be used for different Burkholderia species, for different growth conditions, and it is likely suitable for the use in proteomic studies of other bacteria. Following protein extraction, a two-dimensional (2-D) gel electrophoresis proteomic technique is described to study global changes in the proteomes of these organisms. This method consists of the separation of proteins according to their isoelectric point by isoelectric focusing in the first dimension, followed by separation on the basis of molecular weight by acrylamide gel electrophoresis in the second dimension. Visualization of separated proteins is carried out by silver staining.     

Analysis of mitogenic activity of proteins after separation by gel electrophoresis

We have used a combination of gel electrophoresis and a cell culture assay in microplates to analyse mitogenic activity in tissue extracts. The procedure is a modification of the method described by Kuo et al. The proteins were separated by native gel electrophoresis or isoelectric focusing. The gel was sliced and defined pieces were transferred into tissue culture inserts fitting in 96 well microplates, which contained the test cells. The proteins diffused from the gel slices directly into the culture supernatant and the mitogenic effects were evaluated by a colorimetric assay (MTT or phosphatase activity). Human interleukin 2 was used to demonstrate the feasibility of the method by evaluating the mitogenic effect on the cell line CTLL-2. Extracts of bovine pituitary glands were separated by native gel electrophoresis and isoelectric focusing and several protein bands could be identified which showed a distinct mitogenic effect on human endothelial cells. The method is very sensitive and allows rapid screening of protein mixtures for bioactive fractions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Two dimensional electrophoresis of thylakoid membrane proteins and its application to microsequencing

A procedure of two-dimensional gel electrophoresis adapted for application on membrane proteins from the thylakoids is described. It involves isoelectric focusing in the first dimension and size dependent electrophoresis in the second dimension. About 100 polypeptides are clearly separated with relatively little streaking. About 20 polypeptides are identified by immunoblotting or location in the gel. They are the polypeptides of the PS I core, the 64 kDa protein, the and subunits of CF1 ATPase, cytochrome f, Rieske iron-sulfur protein, the 23 kDa and 33 kDa polypeptides of the oxygen evolving complexes, CP29, CP24, CP27 and CP25 (last two proteins belong to LHCII). Some proteins give rise to two or more separate spots indicating a separation of different isoforms of these proteins. Among them, the LHCII polypeptides (27 kDa and 25 kDa) were each resolved into at least three spots in the pH range 4.75–5.90; the Rieske FeS protein, as published elsewhere (Yu et al. 1994), was separated into two forms having different isoelectric points (pI 5.1 and 5.4), each of them was also microsequenced; the 64 kDa protein claimed to be a LHCII-kinase was found to be multiple forms appearing in at least two isoforms with pI 6.2 (K1) and 6.0 (K2) respectively, furthermore, K1 can be resolved into two subpopulations.The lateral distribution of these proteins in the thylakoid membrane was determined by analysing the vesicles originating from different parts of the thylakoids. The data obtained from this analysis can be partially used as markers for different thylakoid domains.This procedure for sample solubilization and 2-D electrophoresis is useful for the analysis of the polypeptide composition of vesicles originating from the thylakoid membrane and for microsequences of individual polypeptides isolated from the 2-D gel.     

High-throughput peptide mass fingerprinting of soybean seed proteins: automated workflow and utility of UniGene expressed sequence tag databases for protein identification

Identification of anonymous proteins from two-dimensional (2-D) gels by peptide mass fingerprinting is one area of proteomics that can greatly benefit from a simple, automated workflow to minimize sample contamination and facilitate high-throughput sample processing. In this investigation we outline a workflow employing robotic automation at each step subsequent to 2-D gel electrophoresis. As proof-of-concept, 96 protein spots from a 2-D gel were analyzed using this approach. Whole protein (1 mg) from mature, dry soybean (Glycine max [L.] Merr.) cv. Jefferson seed was resolved by high resolution 2-D gel electrophoresis. Approximately 150 proteins were observed after staining with Coomassie Blue. The rather low number of detected proteins was due to the fact that the dynamic range of protein expression was greater than 100-fold. The most abundant proteins were seed storage proteins which in total represented over 60% of soybean seed protein. Using peptide mass fingerprinting 44 protein spots were identified. Identification of soybean proteins was greatly aided by the use of annotated, contiguous Expressed Sequence Tag (EST) databases which are available for public access (UniGene, ftp.ncbi.nih.gov/repository/UniGene/). Searches were orders of magnitude faster when compared to searches of unannotated EST databases and resulted in a higher frequency of valid, high-scoring matches. Some abundant, non seed storage proteins identified in this investigation include an isoelectric series of sucrose binding proteins, alcohol dehydrogenase and seed maturation proteins. This survey of anonymous seed proteins will serve as the basis for future comparative analysis of seed-filling in soybean as well as comparisons with other soybean varieties.     

Electronic Western blot of matrix-assisted laser desorption/ionization mass spectrometric-identified polypeptides from parallel processed gel-separated proteins

Identification of proteins previously separated by one-dimensional (1-D) or two-dimensional gel electrophoresis requires significant manipulations to digest the proteins into their respective peptides and to extract them from the gel prior to mass analysis. This article describes the simultaneous transfer and digestion of proteins directly from 1-D gels onto a membrane ready for matrix-assisted laser desorption/ionization (MALDI) mass spectrometric (MS) analysis. Protein transfer and digestion efficiencies are estimated to be more than 95%. The effectiveness of this procedure is demonstrated by identifying 110 unique proteins derived from a lysate of Escherichia coli and 149 proteins derived from a mouse liver homogenate separated by 1-D sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Using crude mouse liver homogenates, four distinct glutathione S-transferase classes, ranging from 23 to 27 kDa, are identified from a separating gel, indicating the discriminating potential for this method. A Visual Basic program allowed visualization of the identified proteins according to their respective positions on the 1-D gels. In many cases, two or more proteins could be identified within a single band of the SDS gel. The “digital” images generated resemble Western blots without the use of antibodies or signal amplification techniques.     

A nuclear protein associated with cell divisions in plants

A nuclear protein, present in carrot meristems and rapidly proliferating cultured cells of carrot (Daucus carota L.) has been identified by the use of a monoclonal antibody (MAb 21D7). By combining the techniques of two-dimensional polyacrylamide gel analysis and blotting separated proteins onto nitrocellulose sheets, it was shown that the antibody detected a single polypeptide of apparent molecular mass (M _r) of 45000 and an isoelectric focusing point (pI) of 6.7. This protein was found by subcellular fractionation and immunofluorescence to be highly concentrated in the nucleoli of somatic and zygotic embryos of a wide range of plants. It was not detectable in logarthmically growing cells ofEscherichia coli, yeast, embryos ofDrosophila melanogaster or cultured C3H mouse cells. These data indicate that this protein is a highly conserved non-histone protein associated with nuclei of rapidly dividing plant cells.Abbreviations M _r apparent molecular mass - Da dalton - Ig immunoglobulins - MAb monoclonal antibody - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - 2-D gel two-dimensional gel electrophoresis - 2,4-D 2,4-dichlorophenoxyacetic acid     

Two-dimensional reference map of Agrobacterium tumefaciens proteins

Proteomics based on two-dimensional (2-D) gel electrophoresis of proteins followed by spot identification with mass spectrometry is a commonly used method for physiological studies. Physiological proteomics requires 2-D reference maps, on which most of the main proteins are identified. We present a reference map for the bacterial plant pathogen Agrobacterium tumefaciens proteins, which contains more than 300 entries with an isoelectric point (pI) between 4 and 7. The quantitative study of the proteins in the analytical window of the master gel demonstrated unique features, in comparison with other bacteria. In addition, a theoretical analysis of several protein parameters was performed and compared with the experimental results. A comparison of the theoretical molecular weight (MW) of the proteins and their theoretical pI with their vertical and horizontal migration distances, respectively, pointed out the existence of several proteins that strongly diverted from the graph trend-line. These proteins were clearly subjected to post-translational modifications, which changed their pI and/or MW. Additional support for post-translational modifications comes from the identification of multiple spots of the same gene products. Post-translational modifications appear to be more common than expected, at least for soluble proteins, as more than 10% of the proteins were associated with multiple spots.     

Solution phase isoelectric fractionation in the multi-compartment electrolyser: a divide and conquer strategy for the analysis of complex proteomes.

Sample complexity frequently interferes with the analysis of low-abundance proteins by two-dimensional gel electrophoresis (2DGE). Ideally, high abundance proteins should be removed, allowing low-abundance proteins to be applied at much higher concentrations than is possible with the unfractionated sample. One approach is to partition the sample in a manner that segregates the bulk of extraneous proteins from the protein(s) of interest. Solution phase isoelectric focusing in the multi-compartment electrolyser generates fractions of discrete isoelectric point (pI) intervals allowing isolated narrow segments of a proteome to be analysed individually by 2DGE. It is particularly useful for the isolation of low-abundance proteins of extremely basic or acidic pI.     

Global landscape of structural proteins of infectious spleen and kidney necrosis virus

Infectious spleen and kidney necrosis virus (ISKNV), the type species of the genus Megalocytivirus in the family Iridoviridae, causes severe damage to mandarin fish cultures in China. Little is known about the proteins of ISKNV virions. In this study, a total of 38 ISKNV virion-associated proteins were identified by four different workflows with systematic and comprehensive proteomic approaches. Among the 38 identified proteins, 21 proteins were identified by the gel-based workflows (one-dimensional [1-D] and two-dimensional [2-D] gel electrophoresis). Fifteen proteins were identified by 1-D gel electrophoresis, and 16 proteins were identified by 2-D gel electrophoresis, with 10 proteins identified by both methods. Another 17 proteins were identified only by liquid chromatography (LC)-based workflows (LC-matrix-assisted laser desorption ionization [MALDI] and linear trap quadrupole [LTQ]-Orbitrap). Among these 17 LC-identified proteins, 5 proteins were identified uniquely by the LC-MALDI workflow, whereas another 6 proteins were identified only by the LTQ-Orbitrap workflow. These results underscore the importance of incorporation of multiple approaches in identification of viral proteins. Based on viral genomic sequence, genes encoding these 38 viral proteins were cloned and expressed in vitro. Antibodies were produced against these 38 proteins to confirm the ISKNV structural proteins by Western blotting. Of the newly identified proteins, ORF 056L and ORF 118L were identified and confirmed as two novel viral envelope proteins by Western blotting and immunoelectron microscopy (IEM). The ISKNV proteome reported here is currently the only characterized megalocytivirus proteome. The systematic and comprehensive identification of ISKNV structural proteins and their localizations in this study will facilitate future studies of the ISKNV assembly process and infection mechanism.     

Identification and Characterization of Major Lipid Particle Proteins of the Yeast Saccharomyces cerevisiae

Lipid particles of the yeast Saccharomyces cerevisiae were isolated at high purity, and their proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Major lipid particle proteins were identified by mass spectrometric analysis, and the corresponding open reading frames (ORFs) were deduced. In silicio analysis revealed that all lipid particle proteins contain several hydrophobic domains but none or only few (hypothetical) transmembrane spanning regions. All lipid particle proteins identified by function so far, such as Erg1p, Erg6p, and Erg7p (ergosterol biosynthesis) and Faa1p, Faa4p, and Fat1p (fatty acid metabolism), are involved in lipid metabolism. Based on sequence homology, another group of three lipid particle proteins may be involved in lipid degradation. To examine whether lipid particle proteins of unknown function are also involved in lipid synthesis, mutants with deletions of the respective ORFs were constructed and subjected to systematic lipid analysis. Deletion of YDL193w resulted in a lethal phenotype which could not be suppressed by supplementation with ergosterol or fatty acids. Other deletion mutants were viable under standard conditions. Strains with YBR177c, YMR313c, and YKL140w deleted exhibited phospholipid and/or neutral lipid patterns that were different from the wild-type strain and thus may be further candidate ORFs involved in yeast lipid metabolism.     

Use of surface-enhanced laser desorption ionization-time-of-flight to identify heat shock protein 70 isoforms in closely related species of the virilis group of Drosophila

The 70-kDa heat shock protein (Hsp) family in all Drosophila species includes 2 environmentally inducible family members, Hsp70 and Hsp68. Two-dimensional gel electrophoresis revealed an unusual pattern of heat shock-inducible proteins in the species of the virilis group. Trypsin fingerprinting and microsequencing of tryptic peptides using ProteinChip Array technology identified the major isoelectric variants of Hsp70 family, including Hsp68 isoforms that differ in both molecular mass and isoelectric point from those in Drosophila melanogaster. The peculiar electrophoretic mobility is consistent with the deduced amino acid sequence of corresponding hsp genes from the species of the virilis group.