ISSN 10214437, Russian Journal of Plant Physiology, 2011, Vol. 58, No. 4, pp. 575–579. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © I.Yu. Subota, A.Sh. Arziev, Yu.M. Konstantinov, 2011, published in Fiziologiya Rastenii, 2011, Vol. 58, No. 4, pp. 518–522.
All living organisms are capable of receiving and
processing environmental cues. In the living systems,
signaling relies mainly on reversible protein phospho
rylation . A classical signaling cascade based on
protein kinases/phosphatases  resembles a transis
tor and operates as a switch of functions of target pro
teins, which, in turn, results in signal amplification.
Operation of cell protein kinases and protein phos
phatases can be compared to the central unit of a com
puter processor . It recognizes the environmental
cues via sensor and receptor proteins, processes this
information, and then transmits it via various protein
targets to the cellular systems of genetic regulation.
Such transduction results in appropriate changes in
cellular metabolism, ion flux, gene expression, as well
as cell growth and divisions.
About 30% of all proteins in a eukaryotic cell are
phosphorylated . A significant portion of amino
acid residues of a polypeptide chain becomes phos
phorylated and, consequently, the functions of the
protein get changed. Usually, serine, threonine, and
tyrosine residues become phosphorylated at a ratio of
1000 : 100 : 1, respectively .
In silico analysis demonstrated that nuclear
genomes of rice and Arabidopsis encode about 1100 to
1700 protein kinases , which is ten times greater
than the number of protein kinases encoded in the
yeast genome (119)  and twice or thrice greater than
the number found in the human genome (518 protein
kinases) . It is believed that plant mitochondria
contain on average about 50 to 200 protein kinases, a
similar number, or even more, of their protein targets,
and about 10 to 30 protein phosphatases .
Phosphorylation/dephosphorylation of mitochon
drial proteins is considered an important posttransla
tional protein modification mechanism, which partici
pates in numerous cellular signaling pathways, includ
ing the regulation of energetic metabolism and of
mitochondriainduced apoptosis . It was shown that
cAMPdependent protein phosphorylation in mito
chondria of mammals and yeast represents a necessary
stage in signal transduction processes in cells [9, 10].
In our previous study, we have found that such
common intracellular signals like Ca
affect the level of phosphorylation of maize mitochon
drial proteins . It is important to note that protein
phosphorylation in maize mitochondria is redoxsen
sitive . It was suggested that the redoxdependent
phosphorylation/dephosphorylation of mitochondrial
proteins plays an important role in mitochondrial sig
naling in higher plants . Experiments with mito
f Maize Mitochondrial
Proteins with Different Localization
I. Yu. Subota, A. Sh. Arziev, and Yu. M. Konstantinov
Siberian Institute of Plant Physiology and Biochemistry, Siberian Branch of Russian Academy of Sciences, 664033 Irkutsk,
fax: +7 (3952) 510754; email: firstname.lastname@example.org
Received November 24, 2010
—Phosphorylation and dephosphorylation of the proteins residing in the outer mitochondrial mem
brane, mitoplasts and whole mitochondria of maize (
L.) were investigated in order to reveal the pos
sible participation of these processes in mitochondrial signaling. A mitochondrial protein of around 57 kD
was identified by immunocytochemistry as
subunit of the F
ATPase complex. In isolated mitochondria of
maize, phosphorylation of this protein could be visualized only after treating mitochondria with endotholl,
an inhibitor of the PP1a and PP2A protein phosphatases. A phosphorylated protein of 46.6 kD was identified
subunit of the F
ATPase complex. Ca
is the most common second messenger participating in mito
chondrial signaling. We conclude that the transmission of the Ca
signal to the plant mitochondria occurs
via proteins of the outer mitochondrial membrane. The systems perceiving this signal could include the pro
tein phosphatases residing in the outer mitochondrial membrane, which preferentially dephosphorylate the
proteins in the inner membrane.
Keywords: Zea mays
, mitochondria, membranes, phosphorylation/dephosphorylation, intercellular signals,
: HSP—heat shock proteins.