Structural Properties of the Human Acidic Ribosomal P Proteins Forming the P1-P2 Heterocomplex

Abstract

The ribosome has a morphologically distinct structural feature called the stalk, recognized as a vital element for its function. The ribosomal P proteins constitute the main part of the eukaryotic ribosomal stalk, forming a pentameric structure P0-(P1-P2)(2). The group of P1/P2 proteins in eukaryotes is very diverse, and in spite of functional and structural similarities they do not fully complement one another, probably constituting an adaptive feature of the ribosome from a particular species to diverse environmental conditions. The functional differences among the P1/P2 proteins were analysed in vivo several times; however, a thorough molecular characterization was only done for the yeast P1/P2 proteins. Here, we report a biophysical analysis of the human P1 and P2 proteins, applying mass spectrometry, CD and fluorescence spectroscopy, cross-linking and size exclusion chromatography. The human P1/P2 proteins form stable heterodimer, as it is the case for P1/P2 from yeast. However, unlike the yeast complex P1A-P2B, the human P1-P2 dimer showed a three-state transition mechanism, suggesting that an intermediate species may exist in solution.

Molecular cloning of the ribosomal P-proteins MgP1, MgP2, MgP0, and superoxide dismutase (SOD) in the mussel Mytilus galloprovincialis and analysis of MgP0 at stress conditions

“…The stalk is universally composed of a pentameric complex, that in prokaryotes consists of two dimers of 12 kDa acidic proteins L12 and its N-acetylated form L7, and one copy of one larger protein, L10, directly bound to 23S RNA, although heptameres have been reported in archaeas and some thermophilic bacteria (Diaconu et al, 2005;Ilag et al, 2005). The similar eukaryotic pentameric complex P0(P1-P2) 2 is made of four 12-kDa acidic proteins of two types, called P1 and P2 -equivalent to bacterial L7/ L12-and one 32-kDa protein, P0, equivalent to L10 (Grela et al, 2008;Wool et al, 1991). In some eukaryotic species there is more than one member in each P1 and P2 family.…”

In vivo formation of Plasmodium falciparum ribosomal stalk — A unique mode of assembly without stable heterodimeric intermediates

“…Although the parasite individual P-proteins in general reflect the behavior of stalk proteins from other classes of organisms, the reconstruction of the P1-P2 or uL10/P0-P1-P2 complexes using a previously developed in vitro denaturation/renaturation procedure for the P-proteins was found to be unsuccessful. In contrast, it was shown in several reports that in yeast [40,50], human [37], or silkworm [51] heterodimers and pentamers were spontaneously formed in analogous experiments. Our surprising observation got further confirmation in the results of the bacterial two-hybrid experiment.…”

“…It should be pointed out that the behavior of parasite P-proteins resembles that found in other species, where individual P-proteins produced in a heterologous system tend to form oligomers [33][34][35][36]. However, as it was shown previously in yeast, human, and other organisms [8,35,[37][38][39], P-protein folding is a cooperative event, and the P1-P2 dimer is the least, while the uL10/P0-(P1-P2) 2 pentamer the most favorable stable entity of P-proteins. Therefore, we attempted to form a P1-P2 protein complex.…”

“…In order to understand this unique group of proteins, we have taken an integral approach to study the cross-talk among all P. falciparum P-stalk proteins. The molecular behavior of P. falciparum proteins resembles the properties of P-proteins from other species, where individual P-proteins are present in various oligomeric forms in vitro [37,40,47]. Recently, a P2 homo-oligomer was found as a biologically relevant species in P. falciparum [48,49], suggesting that it may represent one of the functional forms of P2 in some stages of parasite development.…”

Solution structure of the natively assembled yeast ribosomal stalk determined by small-angle X-ray scattering

“…The rRNAbinding domain of these proteins is homologous and functionally interchangeable [8]. In turn, the L12/P1-P2 proteins form the functional part of the stalk which is attached to the ribosome through the L10/P0 proteins, as (L12) 2 or P1-P2 dimers [2,[9][10][11]]. An interesting case is found in lower eukaryotes, such as the yeast Saccharomyces cerevisiae, where the two P1/P2 proteins have evolved up to four different proteins, P1A, P1B, P2A and P2B [10,12].…”