Page 79 - The Biochemistry of Inorganic Polyphosphates

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Eukaryotes 63
of cellular PolyP detected by NMR spectroscopy (Beauvoit et al., 1989). PolyP was also
found in a pure mitochondrial fraction of Saccharomyces cerevisiae by chemical extraction
(Pestov et al., 2003). This acid-soluble PolyP, with an average chain length of about 25
phosphate residues, comprised ∼ 7 % of the whole PolyP content of the cell. PolyP was
also observed in mitochondria of mammalian cells (Kornberg et al., 1999).
We have no positive evidence of the presence of PolyPs in chloroplasts. In chloroplasts
of Acetabularia mediaterranea (Rubtsov et al., 1977) and in cotton plants (Valikhanov and
Sagdulaev, 1979), PolyPs were not found.
The presence of specific fractions of high-molecular-weight PolyPs in the nuclei of
different organisms has been demonstrated by many researchers (Penniall and Griffin, 1964;
Goodman et al., 1968; Sauer et al., 1956; Bashirelashi and Dallam, 1970; Kulaev et al.,
1970b; Skryabin et al., 1973; Mansurova et al., 1975a; Offenbacher and Kline, 1984; Pilatus
et al., 1989; Kumble and Kornberg, 1995, 1996).
PolyPs were found in isolated nuclei from N. crassa (Kulaev et al., 1970b). These were
extracted with saturated salt solution (see Table 5.2). The presence of PolyPs in this fraction
was proved exclusively by chromatography. Among the products of partial hydrolysis of this
fraction by using the method of Thilo and Wicker (1957), cyclotriphosphate was found. The
phosphoruscontainedinthesalt-solublenuclearfractionamountedto15%ofthetotalPolyP
phosphorus of the salt-soluble fraction of whole cells. Further purification of the nuclear
fraction by centrifugation under a sucrose gradient or by other methods did not result in the
removal of PolyPs from the nuclei. Similar results were obtained for E. magnusii (Skryabin
et al., 1973). The PolyP content of the nuclei represented over 50 % of the total salt-soluble
PolyP of the whole cells. No other PolyP fractions were found in the nuclei of this organism.
PolyP represented ∼ 13–15 % of the total phosphorus of isolated nuclei.
PolyPs with an average chain length of 100 residues were observed in the nuclei of
Physarium polycephalum (Pilatus et al., 1989). Nuclear preparations of mammalian cells
were found to be relatively enriched in PolyPs (Kumble and Kornberg, 1995; Kornberg,
1999).
Amounts of PolyP in the nuclei might be low; however, these compounds are conserved
thereduringevolution,occurringinthenucleiofboththelowereukaryotesandmammalians.
As a whole, PolyPs in cells of eukaryotes are characterized by plural localization, de-
pending on the cell age or environmental conditions. For example, cytochemical data on
the localization of PolyPs in the cells of Saccharomyces cerevisiae are presented in Figure
5.2, according to Voˇr´ıˇsek et al. (1982). Further studies of this problem may provide new
data on the functions of these biopolymers.