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At least 811 records · Page 45Linked to original sources
PubMed2004

Comparison of the proteome of Methylobacterium extorquens AM1 grown under methylotrophic and nonmethylotrophic conditions.

Methylobacterium extorquens AM1 is a facultative methylotrophic bacterium that is capable of growing in the presence of methanol as the sole carbon and energy source, but is also able to grow on a limited number of C(2), C(3), and C(4) compounds, for example succinate. This study provides a proteomic view of the cellular adaptation of M. extorquens AM1 to growth on methanol and succinate, respectively. Cytosolic proteins were separated by two-dimensional gel electrophoresis employing overlapping pH ranges and visualized by silver nitrate or fluorescence staining. A proteomic reference map containing 229 different proteins identified by peptide mass fingerprinting of tryptic fragments was established. Comparative proteome profiling of methanol- and succinate-grown cells led to the identification of 68 proteins that are induced under methylotrophic growth conditions in comparison to growth on succinate. This group includes most proteins known to be directly involved in methanol oxidation to CO(2) and in assimilation of one carbon units by the serine cycle as well as 18 proteins without any assigned function and two proteins with a predicted regulatory function. Furthermore, the proteome analysis revealed putative isoenzymes for formaldehyde-activating enzyme Fae, malyl-CoA lyase, malate-dehydrogenase, and fumarase, that need to be characterized functionally in future studies.

Bacterial Proteins↗
PubMed2005

Eye lens proteomics: from global approach to detailed information about phakinin and gamma E and F crystallin genes.

Exploration of the lenticular proteome poses a challenging and worthwhile undertaking as cataracts, the products of a disease phenotype elicited by this proteome, remains the leading cause of vision impairment worldwide. The complete ten day old lens proteome of Mus musculus C57BL/6J was resolved into 900 distinct spots by large gel carrier ampholyte based 2-DE. The predicted amino acid sequences of all 16 crystallins ubiquitous in mammals were corroborated by mass spectrometry (MS). In detailed individual spot analyses, the primary structure of the full murine C57BL/6J beaded filament component phakinin CP49 was sequenced by liquid chromatography/electrospray ionization-tandem MS and amended at two positions. This definitive polypeptide sequence was aligned to the mouse genome, thus identifying the entire C57BL/6J genomic coding region. Also, two murine C57/6J polypeptides, both previously classified as gamma F crystallin, were clearly distinguished by MS and electrophoretic mobility. Both were assigned to their respective genes, one of the polypeptides was reclassified as C57BL/6J gamma E crystallin. Building on these data and previous investigations an updated crystallin reference map was put forth and several non crystallin lenticular components were examined. These results represent the first part of a comprehensive investigation of the mouse lens proteome (http://www.mpiib-berlin.mpg.de/2D-PAGE) with emphasis on understanding genetic effects on proteins and disease development.

Amino Acid Sequence↗
PubMed2003

Proteomic analysis of Lactococcus lactis, a lactic acid bacterium.

Lactococcus lactis is a Gram-positive bacteria, which belongs to the group of lactic acid bacteria among which several genera play an essential role in the manufacture of food products. Cytosolic proteins of L. lactis IL1403 cultivated in M17 broth have been resolved by two-dimensional gel electrophoresis using two pH gradients (pH 4-7, 4.5-5.5). More than 230 spots were identified by peptide mass fingerprints, corresponding to 25% of the predicted acid proteome. The present study made it possible to describe at the proteome level a significant number of cellular pathways (glycolysis, fermentation, nucleotide metabolism, proteolysis, fatty acid and peptidoglycan synthesis) related to important physiological processes and technological properties. It also indicated that the fermentative metabolism, which characterizes L. lactis is associated with a high expression of glycolytic enzymes. Thirty-four proteins were matched to open reading frames for which there is no assigned function. The comparison at the proteome level of two strains of L. lactis showed an important protein polymorphism. The comparison of the proteomes of glucose- and lactose-grown cells revealed an unexpected link between the nature of the carbon source and the metabolism of pyrimidine nucleotides.

Bacterial Proteins↗
PubMed2003

Evaluation of ethanol-fixed, paraffin-embedded tissues for proteomic applications.

We previously reported that ethanol fixation and paraffin embedding of tissues produce excellent histomorphology and good preservation of macromolecules. Here, we present a detailed evaluation of ethanol-fixed tissues for proteomic initiatives. When proteins were extracted from ethanol-fixed, paraffin-embedded prostate tissue, resolved by two-dimensional gel electrophoresis (2-DE), and stained by standard methods, several hundred protein molecules could be detected and successfully analyzed by mass spectrometry. Protein profiles obtained from ethanol-fixed tissues were highly similar to those observed from frozen tissues, in contrast to the poor protein recovery from formalin-fixed material. The protein content of specific cells that were microdissected from ethanol-fixed tissue sections using laser capture microdissection could also be successfully analyzed by 2-DE. We observed that eosin staining of tissue sections had a detrimental effect on protein separation, whereas hematoxylin staining had minimal consequence. In order to illustrate the applicability of ethanol-fixed tissues for proteomic discovery studies, we compared the protein profiles of patient-matched, normal prostatic epithelial cells and invasive adenocarcinoma cells obtained from ethanol-fixed, paraffin-embedded tissues. A number of differentially expressed proteins was discovered and identified by mass spectrometry. Immunohistochemical analyses performed on ethanol-fixed tissue sections were in agreement with the proteomic discovery findings. In light of these results, we conclude that ethanol-fixed tissues can be successfully utilized for proteomic analyses.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2003

Use of serological proteomic methods to find biomarkers associated with breast cancer.

New technologies for the detection and therapy of early stage breast cancer are urgently needed. Pathological changes in breast might be reflected in proteomic patterns in serum. A proteomic tool was used to identify proteomic patterns in serum that distinguishes neoplastic from non-neoplastic disease within the breast. Preliminary results derived from the serum analysis from 54 unaffected women and 76 patients with breast cancer were analyzed by two-dimensional (2-D) electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry, HSP27 was found up-regulated while 14-3-3 sigma was down-regulated in the serum of breast cancer patients. The two protein biomarkers were then used to classify an independent set of 104 masked serum samples. The results showed that the protein pattern on 2-D gels can completely segregate the serum of breast cancer from non-cancer. The discriminatory pattern correctly identified all 69 breast cancer cases in the masked set. Of the 35 cases of non-malignant disease, 34 were recognized as non-cancer. These findings justify a prospective population-based assessment of proteomic technology as a screening or diagnostic tool for breast cancer in high-risk and general populations. These two protein biomarkers could also be used as targets for further study in drug design and breast cancer therapy.

Adult↗
PubMed2005

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).

Bacterial Proteins↗
PubMed2005

Pressure overload and neurohumoral activation differentially affect the myocardial proteome.

Treatment with monocrotaline causes pulmonary hypertension in rats. This results in severe pressure overload-induced hypertrophy of the right ventricles, whilst the normally loaded left ventricles do not hypertrophy. Both ventricles are affected by enhanced neuroendocrine stimulation in this model. We analyzed in this model load-induced and catecholamine-induced changes of right and left ventricular proteome by two-dimensional gel electrophoresis, tryptic in-gel digest, and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. All analyzed animals showed right ventricular hypertrophy without signs of heart failure. Changes of 27 proteins in the right and 21 proteins in the left ventricular myocardium were found. Given the hemodynamic features of this animal model, proteome changes restricted to the right ventricle are caused by pressure overload. We describe for the first time a potentially novel pathway (BRAP2/BRCA1) that is involved in myocardial hypertrophy. Furthermore, we demonstrate that increased afterload-induced hypertrophy leads to striking changes in the energy metabolism with down-regulation of pyruvate dehydrogenase (subunit beta E1), isocitrate dehydrogenase, succinyl coenzyme A ligase, NADH dehydrogenase, ubiquinol-cytochrome C reductase, and propionyl coenzyme A carboxylase. These changes go in parallel with alterations of the thin filament proteome (troponin T, tropomyosin), probably associated with Ca(2+) sensitization of the myofilaments. In contrast, neurohumoral stimulation of the left ventricle increases the abundance of proteins relevant for energy metabolism. This study represents the first in-depth analysis of global proteome alterations in a controlled animal model of pressure overload-induced myocardial hypertrophy.

Amino Acid Sequence↗
PubMed2005

Microarrays based on affinity-tagged single-chain Fv antibodies: sensitive detection of analyte in complex proteomes.

Protein-based microarrays are among the novel class of rapidly emerging proteomic technologies that will allow us to efficiently perform global proteome analysis. However, the process of designing adequate protein microarrays is a major inherent problem. In this study, we have evaluated a protein microarray platform based on nonpurified affinity-tagged single-chain (sc) Fv antibody fragments to generate proof-of-principle and to demonstrate the specificity and sensitivity of the array design. To this end, we used our human recombinant scFv antibody library genetically constructed around one framework, the n-CoDeR library containing 2 x 10(10) clones, as a source for our probes. The probes were immobilized via engineered C-terminal affinity tags, his- or myc-tags, to either Ni(2+)-coated slides or anti-tag antibody coated substrates. The results showed that highly functional microarrays were generated and that nonpurified scFvs readily could be applied as probes. Specific and sensitive microarrays were obtained, providing a limit of detection in the pM to fM range, using fluorescence as the mode of detection. Further, the results showed that spotting the analyte on top of the arrayed probes, instead of incubating the array with large sample volumes (333 pL vs. 40 microL), could reduce the amount of analyte required 4000 times, from 1200 attomole to 300 zeptomole. Finally, we showed that a highly complex proteome, such as human sera containing several thousand different proteins, could be directly fluorescently labeled and successfully analyzed without compromising the specificity and sensitivity of the antibody microarrays. This is a prerequisite for the design of high-density antibody arrays applied in high-throughput proteomics.

Humans↗
PubMed2004

Establishment of a near-standard two-dimensional human urine proteomic map.

A proteomic map for human urine on two-dimensional (2-D) gels has been developed. Initial studies demonstrated that the urine proteins prepared by conventional methods showed interference and poor reproducibility in 2-D electrophoresis (2-DE). To address this issue, urine samples were dialyzed to remove any interfering molecules. The dialysis of urine proteins and the concentration by lyophilization without fractionation significantly improved the reproducibility and resolution and likely represents the total urine proteins on a 2-D gel. In addition, removing albumin from urine using Affi-Gel Blue helped to identify the low-abundant proteins. Using the developed method, we prepared proteins from urine collected from healthy females and males. The large inter- and intra-subject variation in protein profiles on 2-D gels made it difficult to establish a normal human urine proteomic 2-D map. To resolve this problem, urinary proteins were prepared from the pooled urine collected from 20 healthy females and males, respectively. The established male and female urine proteomes separated on 2-D gels were almost identical except for some potential sex-dependent protein spots. We have annotated 113 different proteins on the 2-D gel by peptide mass fingerprinting (PMF). We propose that the established total urine proteome can be used for 2-DE analysis, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and identification of novel disease-specific biomarkers.

Albumins↗
PubMed2004

Proteome analysis of red deer antlers.

Deer antlers are the only mammalian organs capable of repeated regeneration. Although antlers are known to develop from pedicles, which arise from antlerogenic cells of cranial periosteum, their developmental process is not fully elucidated. For example, while endocrine and environmental factors influence the antler development, it is still unclear which signaling pathways are involved in the transduction of such stimuli. To study the developmental process of antlers and identify proteins functioning in their growth, we have established proteome maps of red deer (Cervus elaphus) antlers. With two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization mass spectrometry, we analyzed more than 800 protein spots and identified approximately 130 individual proteins derived from the growing tip of antlers. The overall profile of the antler proteome was dissimilar to those of other types of tissue. Also comparison of proteomes derived from proximal bony tissue and the growing tip of antlers revealed substantial differences. Moreover several cell growth or signaling-related proteins are expressed exclusively in the growing tip, suggesting that these proteins function in the growth and differentiation of antlers. Currently, using the antler proteome maps, we are actively searching for the regulatory factor(s) that may control the antler development.

Animals↗
PubMed2005

Large-scale identification of proteins in human salivary proteome by liquid chromatography/mass spectrometry and two-dimensional gel electrophoresis-mass spectrometry.

Human saliva contains a large number of proteins and peptides (salivary proteome) that help maintain homeostasis in the oral cavity. Global analysis of human salivary proteome is important for understanding oral health and disease pathogenesis. In this study, large-scale identification of salivary proteins was demonstrated by using shotgun proteomics and two-dimensinal gel electrophoresis-mass spectrometry (2-DE-MS). For the shotgun approach, whole saliva proteins were prefractionated according to molecular weight. The smallest fraction, presumably containing salivary peptides, was directly separated by capillary liquid chromatography (LC). However, the large protein fractions were digested into peptides for subsequent LC separation. Separated peptides were analyzed by on-line electrospray tandem mass spectrometry (MS/MS) using a quadrupole-time of flight mass spectrometer, and the obtained spectra were automatically processed to search human protein sequence database for protein identification. Additionally, 2-DE was used to map out the proteins in whole saliva. Protein spots 105 in number were excised and in-gel digested; and the resulting peptide fragments were measured by matrix-assisted laser desorption/ionization-mass spectrometry and sequenced by LC-MS/MS for protein identification. In total, we cataloged 309 proteins from human whole saliva by using these two proteomic approaches.

Chromatography, Liquid↗
PubMed2005

Expanding the proteome two-dimensional gel electrophoresis reference map of human renal cortex by peptide mass fingerprinting.

Proteomics methodologies hold great promise in basic renal research and clinical nephrology. The classical approach for proteomic analysis couples two-dimensional gel electrophoresis (2-DE) with protein identification by mass spectrometry, to produce more global information regarding normal protein expression and alterations in different physiological and pathological states. In this report we have expanded the identification of proteins in the renal cortex, improving the previously published map to facilitate the study of different diseases affecting the human kidney. About 250 spots were analyzed by peptide mass fingerprinting, 89 proteins and 74 isoforms for some of them were identified and implemented in the normal human renal cortex 2-DE reference map. This more comprehensive view of the proteome of the human renal cortex could be of invaluable help to the differential proteomic display of urological diseases.

Databases, Protein↗
PubMed2005

Clinical-scale high-throughput human plasma proteome analysis: lung adenocarcinoma.

Clinical proteomics requires the stable and reproducible analysis of a large number of human samples. We report a high-throughput comprehensive protein profiling system comprising a fully automated, on-line, two-dimensional microflow liquid chromatography/tandem mass spectrometry (2-D microLC-MS/MS) system for use in clinical proteomics. A linear ion-trap mass spectrometer (ITMS) also known as a 2-D ITMS instrument, which is characterized by high scan speed, was incorporated into the microLC-MS/MS system in order to obtain highly improved sensitivity and resolution in MS/MS acquisition. This system was used to evaluate bovine serum albumin and human 26S proteasome. Application of these high-throughput microLC conditions and the 2-D ITMS resulted in a 10-fold increase in sensitivity in protein identification. Additionally, peptide fragments from the 26S proteasome were identified three-fold more efficiently than by the conventional 3-D ITMS instrument. In this study, the 2-D microLC-MS/MS system that uses linear 2-D ITMS has been applied for the plasma proteome analysis of a few samples from healthy individuals and lung adenocarcinoma patients. Using the 2-D and 1-D microLC-MS/MS analyses, approximately 250 and 100 different proteins were detected, respectively, in each HSA- and IgG-depleted sample, which corresponds to only 0.4 microL of blood plasma. Automatic operation enabled the completion of a single run of the entire 1-D and 2-D microLC-MS/MS analyses within 11 h. Investigation of the data extracted from the protein identification datasets of both healthy and adenocarcinoma groups revealed that several of the group-specific proteins could be candidate protein disease markers expressed in the human blood plasma. Consequently, it was demonstrated that this high-throughput microLC-MS/MS protein profiling system would be practically applicable to the discovery of protein disease markers, which is the primary objective in clinical plasma proteome projects.

Adenocarcinoma↗
PubMed2005

Proteome analysis reveals adaptation of Pseudomonas aeruginosa to the cystic fibrosis lung environment.

Pseudomonas aeruginosa is known for the chronic lung colonization of cystic fibrosis (CF) patients in addition to eye, ear and urinary tract infections. With the underlying disease CF patients are predisposed to P. aeruginosa chronic lung infection, which leads to morbidity and mortality. In this study, we compared the protein expression profile of a CF lung-adapted P. aeruginosa strain C with that of the burn-wound isolate PAO. Differentially expressed proteins from the whole-cell, membrane, periplasmic as well as extracellular fraction were identified. The whole-cell proteome of strain C showed down-regulation of several proteins involved in amino acid metabolism, fatty acid metabolism, energy metabolism and adaptation leading to a highly distinct proteome pattern for strain C in comparison to PAO. Analysis of secreted proteins by strain C compared to PAO revealed differential expression of virulence factors under non-inducing conditions. The membrane proteome of strain C showed modulation of the expression of porins involved in nutrient and antibiotic influx. The proteome of the periplasmic space of strain C showed retention of elastase despite that the equal amounts were secreted by strain C and PAO. Altogether, our results elucidate adaptive strategies of P. aeruginosa towards the nutrient-rich CF lung habitat during the course of chronic colonization.

Adaptation, Physiological↗
PubMed2005

Global protein expression pattern of Bradyrhizobium japonicum bacteroids: a prelude to functional proteomics.

As a prelude to using functional proteomics towards understanding the process of symbiotic nitrogen fixation between the legume soybean and the soil bacteria Bradyrhizobium japonicum, we examined the total protein expression pattern of the nodule bacteria, often referred to as bacteroids. A partial proteome map was constructed by separating the total bacteroid proteins using high-resolution 2-DE. Of the several hundred protein spots analyzed using PMF, 180 spots were tentatively identified by searching the available database for B. japonicum, (http://www.kazusa.or.jp/index.html). The data showed that the bacteroid expressed a dominant and elaborate protein network for nitrogen and carbon metabolism, which is closely dependent on the plant supplied metabolites, and seems aptly supported by a selective group of bacteroid transporter proteins. However, they seem to lack a defined fatty acid and nucleic acid metabolism. Interestingly, the proteins related to protein synthesis, scaffolding and degradation were among the most predominant spots of the bacteroid proteome. In addition, several proteins, which showed fairly good expression, were identified to be involved with cellular detoxification, stress regulation and signaling communication components. This preliminary proteomic data matches very well with several biochemical and genetic reports, and clearly shows the inter-connection between several metabolic pathways that meet the needs of the bacteroid. It is expected that in the future this will allow us to develop testable hypotheses about the roles of several of these proteins in context to the metabolic pathway connections and metabolite fluxes.

Amino Acids↗
PubMed2005

Do we want our data raw? Including binary mass spectrometry data in public proteomics data repositories.

With the human Plasma Proteome Project (PPP) pilot phase completed, the largest and most ambitious proteomics experiment to date has reached its first milestone. The correspondingly impressive amount of data that came from this pilot project emphasized the need for a centralized dissemination mechanism and led to the development of a detailed, PPP specific data gathering infrastructure at the University of Michigan, Ann Arbor as well as the protein identifications database project at the European Bioinformatics Institute as a general proteomics data repository. One issue that crept up while discussing which data to store for the PPP concerns whether the raw, binary data coming from the mass spectrometers should be stored, or rather the more compact and already significantly processed peak lists. As this debate is not restricted to the PPP but relates to the proteomics community in general, we will attempt to detail the relative merits and caveats associated with centralized storage and dissemination of raw data and/or peak lists, building on the extensive experience gained during the PPP pilot phase. Finally, some suggestions are made for both immediate and future storage of MS data in public repositories.

Computational Biology↗
PubMed2006

Analysis of the Pasteurella multocida outer membrane sub-proteome and its response to the in vivo environment of the natural host.

This study describes the identification of outer membrane proteins (OMPs) of the bacterial pathogen Pasteurella multocida and an analysis of how the expression of these proteins changes during infection of the natural host. We analysed the sarcosine-insoluble membrane fractions, which are highly enriched for OMPs, from bacteria grown under a range of conditions. Initially, the OMP-containing fractions were resolved by 2-DE and the proteins identified by MALDI-TOF MS. In addition, the OMP-containing fractions were separated by 1-D SDS-PAGE and protein identifications were made using nano LC MS/MS. Using these two methods a total of 35 proteins was identified from samples obtained from organisms grown in rich culture medium. Six of the proteins were identified only by 2-DE MALDI-TOF MS, whilst 17 proteins were identified only by 1-D LC MS/MS. We then analysed the OMPs from P. multocida which had been isolated from the bloodstream of infected chickens (a natural host) or grown in iron-depleted medium. Three proteins were found to be significantly up-regulated during growth in vivo and one of these (Pm0803) was also up-regulated during growth in iron-depleted medium. After bioinformatic analysis of the protein matches, it was predicted that over one third of the combined OMPs predicted by the bioinformatics sub-cellular localisation tools PSORTB and Proteome Analyst, had been identified during this study. This is the first comprehensive proteomic analysis of the P. multocida outer membrane and the first proteomic analysis of how a bacterial pathogen modifies its outer membrane proteome during infection.

Animals↗
PubMed2006

Insights into the membrane proteome of rat liver peroxisomes: microsomal glutathione-S-transferase is shared by both subcellular compartments.

Peroxisomes are ubiquitous "multipurpose" organelles of eukaryotic cells. Their matrix enzymes catalyze mainly catabolic and anabolic reactions of lipid metabolism, thus contributing to the regulation of lipid homeostasis. Since most metabolites must be actively transported across the peroxisomal membrane and since individual proteins and protein complexes play functional roles in such transport processes, we analyzed the peroxisomal membrane proteome. Benzyldimethyl-n-hexadecylammoniumchloride (16-BAC)/SDS-2-D-PAGE and mass spectrometry were used to characterize the proteomes of highly purified "light" and "heavy" peroxisomes of rat liver obtained by density gradient centrifugation. In both populations, the major integral membrane proteins could be detected in high concentrations, verifying 16-BAC/SDS-2-D-PAGE as a suitable tool for the preparation of membrane proteomes destined for mass spectrometric analysis. Both reliable and reproducible detection of a distinct set of microsomal (ER) membrane proteins, including microsomal glutathione-S-transferase (mGST), in light and heavy peroxisomal fractions was also possible. Compared with the abundance of most microsomal membrane proteins, we found mGST to be specifically enriched in peroxisomal membrane fractions. Furthermore, C terminus epitope-tagged mGST versions were localized at least in part to peroxisomes in different mammalian cell lines. Taken together, these data suggest that the peroxisomal GST is not a mere ER-contaminant, but a bona fide protein comprising the membrane proteome of both intracellular compartments. In addition, we could detect several mitochondrial proteins in light peroxisome fractions. This finding may likely indicate a physical association of light peroxisomes with mitochondria, since the organelles could be partly separated by mechanical stress. Whether this association is of functional importance awaits further investigation.

Animals↗