title: A possible role of intracellular isoelectric focusing in the evolution of eukaryotic cells and multicellular organisms.
abstract: A new scenario of the origin of eukaryotic cell and multicellularity is presented. A concentric pH-gradient has been shown to exist in the cytosol of eukaryotic cells. The most probable source of such gradient is its self-formation in gradient of electric field between center and periphery of a cell. Theoretical analysis has shown that, for example, a cell of Saccharomyces cerevisiae has enough energy to continuously sustain such gradient of strength about 1.5 kV/cm, the value sufficient for effective isoelectric focusing of cytoplasmic proteins. Focusing of enzymes could highly increase the effectiveness of an otherwise diffusion-limited metabolism of large cells by concentrating enzymes into small and distinct parts of a cytoplasm. By taking away an important physical constraint to the volume of cytoplasm, the intracellular isoelectric focusing enabled evolution of cells 3-4 order of magnitude larger than typical prokaryotic cells. This opened the way for the origin of phagocytosis and lately for the development of different forms of endosymbiosis, some of them resulting in an endosymbiotic origin of mitochondria and plastids. The large volume of a cell-enabled separation of nuclear and cytoplasmic compartments which was a precondition for separation of transcription and translation processes and therefore also for the origin of various RNA-preprocessing mechanisms. The possibility to regulate gene expression by postprocessing RNA and to regulate metabolism by an electrophoretic translocation enzymes between different parts of cytoplasm by changing their isoelectric points opened the way for cell and tissue differentiation and therefore for the origin of complex multicellular organisms.
authors.affiliation: Department of Philosophy and History of Science, Charles University, Vinicná 7, 128 44, Praha 2, Czech Republic. flegr@cesnet.cz
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Flegr
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002468:Cell Physiological Phenomena; D003593:Cytoplasm / Q000502:physiology; D005057:Eukaryotic Cells / Q000166:cytology / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D008954:Models, Biological; D011506:Proteins / Q000502:physiology
chemical_list: D011506:Proteins
references.citation: J Cell Biol. 1977 Dec;75(3):807-17
references.pmid: 925081
references.citation: Nature. 1998 Mar 5;392(6671):37-41
references.pmid: 9510246
references.citation: Life Sci. 1985 Jan 28;36(4):299-307
references.pmid: 4038419
references.citation: Biosystems. 1985;18(2):135-9
references.pmid: 3907730
references.citation: Biochem J. 1994 Mar 1;298 ( Pt 2):313-20
references.pmid: 8135736
references.citation: Biosystems. 1990;24(2):127-33
references.pmid: 2249006
references.citation: Annu Rev Phytopathol. 2003;41:429-53
references.pmid: 12730399
references.citation: Biochim Biophys Acta. 1984 Sep 27;766(3):679-84
references.pmid: 6089881
references.citation: Trends Biochem Sci. 1988 Feb;13(2):43-6
references.pmid: 3238749
references.citation: Cell Biochem Funct. 1996 Dec;14(4):237-48
references.pmid: 8952042
references.citation: J Cell Biol. 1983 Oct;97(4):1249-54
references.pmid: 6684663
references.citation: Electrophoresis. 1995 Jun;16(6):1010-5
references.pmid: 7498121
references.citation: Exp Cell Res. 1980 Jun;127(2):397-408
references.pmid: 6892899
references.citation: Annu Rev Microbiol. 1996;50:317-48
references.pmid: 8905083
references.citation: FEBS Lett. 1983 Jun 13;156(2):227-30
references.pmid: 6852257
references.citation: J Theor Biol. 1986 Feb 21;118(4):443-69
references.pmid: 3713219
references.citation: Biochem J. 1978 Jan 15;170(1):103-14
references.pmid: 629769
references.citation: J Cell Biol. 1983 Oct;97(4):1207-13
references.pmid: 6684662
references.citation: Phys Biol. 2006 May 16;3(2):101-6
references.pmid: 16829696
references.citation: Riv Biol. 2002 May-Aug;95(2):258-72
references.pmid: 12449684
references.citation: Ann N Y Acad Sci. 1973 Jun 15;209:11-22
references.pmid: 4577168
references.citation: Biophys J. 2007 Mar 15;92(6):2108-19
references.pmid: 17208984
references.citation: Biochim Biophys Acta. 1981 Nov 9;639(1):53-76
references.pmid: 7030398
references.citation: Nature. 1987 Jan 29-Feb 4;325(6103):447-50
references.pmid: 3808046
references.citation: Trends Biochem Sci. 1994 May;19(5):193-7
references.pmid: 8048159
references.citation: Biochemistry. 1979 Oct 16;18(21):4487-99
references.pmid: 40590