The concentration of l-leucine could be a trigger for the Lrp-dependent regulation of genes that function during feast or famine (Calvo & Matthews, 1994). Because l-methionine is a key metabolite in the sulphur, methylation and trans-sulphuration pathways, the accumulation of its oxidized forms may significantly perturb cell metabolism. Thus, both l-leucine hydroxylation and l-methionine oxidation could be also involved in the metabolic regulatory network. The authors thank Ms N.Y. Rushkevich for help in gene cloning. “
“In

Colpoda cucullus, the morphogenetic transformation was preceded by an enhancement of the in vivo protein phosphorylation level. Immunofluorescence microscopy using antiphosphoserine antibody showed that these Bortezomib phosphorylated proteins

were localized in the macronucleus and other cytoplasmic regions. Biotinylated Phos-tag/ECL assays of isolated macronuclei showed that a 33-kDa protein (p33) was localized within them. The p33 obtained from isolated macronuclei was tentatively identified as ribosomal P0 protein by LC-MS/MS analysis. In addition, among the encystment-specific phosphoproteins obtained by phosphate-affinity chromatography, the 29-, 31-, and INK 128 purchase 33-kDa proteins (p29, p31, and p33) were tentatively identified as ribosomal P0 protein, whereas the 24-kDa phosphoprotein (p24) was tentatively identified as ribosomal S5 protein. The resting cyst formation (encystment) of protozoans is a kind of cryptobiosis that involves a drastic cellular morphogenesis. The molecular mechanism of cellular differentiation during en- and excystment has been studied especially extensively in parasitic protozoans. For example, encystment-specific key proteins such as cysteine peptidase (Ebert et al., 2008), serine protease (Moon et al., 2008), and enolase (Bouyer et al., 2009; Segovia-Gamboa et al., 2010, 2011) have recently been identified in Acanthamoeba or Entamoeba. In Giardia, proteins such as cyst wall proteins, cyst wall glycopolymer biosynthetic enzymes, transcription factors, and signaling proteins have been reported to play a

role in cellular differentiation during encystment (Lauwaet et al., 2007b; Carranza & Lujan, 2010; and references GPX6 therein). In signal transduction pathways leading to en- or excystment, protein phosphorylation and dephosphorylation were shown to occur (Abel et al., 2001; Slavin et al., 2002; Ellis et al., 2003; Gibson et al., 2006; Bazán-Tejeda et al., 2007; Lauwaet et al., 2007a; Alvarado & Wasserman, 2010), and phosphorylated proteins such as 14-3-3 protein and 70-kDa heat shock protein have been shown to play a role (Alvarado & Wasserman, 2010). In free-living ciliates, on the other hand, the morphogenetic transformation that occurs during en- and excystment is poorly understood at the molecular level, although it is known that the encystment is gene-regulated (Grisvard et al.