Protein oligomerization: How and why

Ali, Mayssam H.; Imperiali, Barbara

doi:10.1016/j.bmc.2005.05.037

Cited by 319 publications

(213 citation statements)

References 102 publications

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“…As PhaP requires both ␣-helices for correct oligomerization, the tertiary structure most likely resembles a doughnut formed by the eight ␣-helices. For thermodynamic reasons, partially hydrophobic surfaces are often involved in the formation of tertiary structures, aiding oligomerization (55,56). As a consequence several modes of interaction of tetrameric PhaP with the PHB granule are conceivable.…”

Section: Resultsmentioning

confidence: 99%

Photoautotrophic Polyhydroxybutyrate Granule Formation Is Regulated by Cyanobacterial Phasin PhaP in Synechocystis sp. Strain PCC 6803

Hauf

Watzer

Roos

et al. 2015

Appl Environ Microbiol

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Cyanobacteria are photoautotrophic microorganisms which fix atmospheric carbon dioxide via the Calvin-Benson cycle to produce carbon backbones for primary metabolism. Fixed carbon can also be stored as intracellular glycogen, and in some cyanobacterial species like Synechocystis sp. strain PCC 6803, polyhydroxybutyrate (PHB) accumulates when major nutrients like phosphorus or nitrogen are absent. So far only three enzymes which participate in PHB metabolism have been identified in this organism, namely, PhaA, PhaB, and the heterodimeric PHB synthase PhaEC. In this work, we describe the cyanobacterial PHA surface-coating protein (phasin), which we term PhaP, encoded by ssl2501. Translational fusion of Ssl2501 with enhanced green fluorescent protein (eGFP) showed a clear colocalization to PHB granules. A deletion of ssl2501 reduced the number of PHB granules per cell, whereas the mean PHB granule size increased as expected for a typical phasin. Although deletion of ssl2501 had almost no effect on the amount of PHB, the biosynthetic activity of PHB synthase was negatively affected. Secondary-structure prediction and circular dichroism (CD) spectroscopy of PhaP revealed that the protein consists of two ␣-helices, both of them associating with PHB granules. Purified PhaP forms oligomeric structures in solution, and both ␣-helices of PhaP contribute to oligomerization. Together, these results support the idea that Ssl2501 encodes a cyanobacterial phasin, PhaP, which regulates the surface-to-volume ratio of PHB granules. C yanobacteria are photosynthetic microorganisms capable of oxygenic photosynthesis. ATP and reduction equivalents derived from photosynthetic electron flow are utilized to fix carbon dioxide and generate 3-phosphoglycerate (1). This metabolite can be utilized for either gluconeogenesis or glycolysis, providing the necessary carbon skeletons for biosynthesis of amino acids and other metabolites required for cell growth (2), when growth conditions are suitable and nutrients are abundant. In fact, carbon flux is greatly affected by the availability of macronutrients like nitrogen (3-5) and phosphorus, which may limit growth (6). Under nutrient-limiting conditions, cyanobacteria undergo a stress adaptation process termed chlorosis (7). This process leads to the degradation of light-harvesting complexes, causing reduced photosynthetic activity and thereby reduced metabolic activity (8). Furthermore, carbon flux is redirected toward glycogen synthesis upon macronutrient starvation (5). In addition, some cyanobacterial strains like Synechocystis sp. strain PCC 6803 (referred to here as Synechocystis) accumulate polyhydroxybutyrate (PHB) as a carbon and redox storage compound (9). PHB is synthesized in three biosynthetic steps, and all three enzymes catalyzing the reactions are known (10, 11). The first step involves a condensation of two acetyl coenzyme A (acetyl-CoA) groups to acetoacetyl-CoA by PhaA (slr1993). In the second step, PhaB (slr1994) reduces acetoacetyl-CoA to hydroxybutyryl-CoA, utilizing NADPH...

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Section: Resultsmentioning

confidence: 99%

Photoautotrophic Polyhydroxybutyrate Granule Formation Is Regulated by Cyanobacterial Phasin PhaP in Synechocystis sp. Strain PCC 6803

Hauf

Watzer

Roos

et al. 2015

Appl Environ Microbiol

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“…Although it has been recognized that protein oligomerization plays a key role in the regulation of proteins, conferring several functional advantages, such as improved stability, increased enzymatic activity, and selective sensitivity to inhibitors (46)(47)(48), the role of oligomerization leading to functional diversification has not been analyzed previously. The formation of hetero-oligomeric isozymes could be a common theme in the mechanisms leading to the retention and subfunctionalization of duplicated genes.…”

Section: Discussionmentioning

confidence: 99%

Diversification of Paralogous α-Isopropylmalate Synthases by Modulation of Feedback Control and Hetero-Oligomerization in Saccharomyces cerevisiae

et al. 2015

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Production of ␣-isopropylmalate (␣-IPM) is critical for leucine biosynthesis and for the global control of metabolism. The budding yeast Saccharomyces cerevisiae has two paralogous genes, LEU4 and LEU9, that encode ␣-IPM synthase (␣-IPMS) isozymes.Little is known about the biochemical differences between these two ␣-IPMS isoenzymes. Here, we show that the Leu4 homodimer is a leucine-sensitive isoform, while the Leu9 homodimer is resistant to such feedback inhibition. The leu4⌬ mutant, which expresses only the feedback-resistant Leu9 homodimer, grows slowly with either glucose or ethanol and accumulates elevated pools of leucine; this phenotype is alleviated by the addition of leucine. Transformation of the leu4⌬ mutant with a centromeric plasmid carrying LEU4 restored the wild-type phenotype. Bimolecular fluorescent complementation analysis showed that Leu4-Leu9 heterodimeric isozymes are formed in vivo. Purification and kinetic analysis showed that the hetero-oligomeric isozyme has a distinct leucine sensitivity behavior. Determination of ␣-IPMS activity in ethanol-grown cultures showed that ␣-IPM biosynthesis and growth under these respiratory conditions depend on the feedback-sensitive Leu4 homodimer. We conclude that retention and further diversification of two yeast ␣-IPMSs have resulted in a specific regulatory system that controls the leucine-␣-IPM biosynthetic pathway by selective feedback sensitivity of homomeric and heterodimeric isoforms. The Leu4 and Leu9 ␣-isopropylmalate synthases (␣-IPMSs), paralogous isozymes from Saccharomyces cerevisiae, catalyze the first committed step of leucine biosynthesis: the synthesis of ␣-isopropylmalate (␣-IPM) from acetyl coenzyme A (acetylCoA) and ␣-ketoisovalerate (␣-KIV). This reaction is carried out in the mitochondria (1-8), and ␣-IPM is then transported from the mitochondria to the cytosol by the yeast oxaloacetate/sulfate carrier Oac1 (9). The concerted action of Leu1 and Leu2 converts ␣-IPM to ␣-ketoisocaproate, the immediate precursor of leucine; these reactions are performed in the cytoplasm (8). The last step in leucine biosynthesis is carried out on both the mitochondria and the cytoplasm through the action of the differentially localized Bat1 or Bat2 aminotransferase (10) (Fig. 1). Most of the ␣-IPMS activity in wild-type S. cerevisiae cells is provided by the mitochondrially localized LEU4-encoded isozyme and not by the Leu4 (Leu4 s) isoform, which naturally lacks the mitochondrial import sequence and is thus localized in the cytosol (1, 2).Leu4 enzymatic activity is inhibited by leucine and CoA, and the amino acid residues responsible for this property have been identified (7). Although no detailed biochemical characterization of the LEU9-encoded isozyme has been performed, it has been shown that it is less sensitive to leucine inhibition than Leu4 is (3).It is noteworthy that the leucine biosynthesis intermediate ␣-IPM plays a dual cellular role. On the one hand, it acts as an intermediate in leucine biosynthesis (5, 6), and on the other, it acts as t...

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“…Many proteins use oligomerization to maintain structural stability, to increase reactivity, to transmit signals or to transport reagents across the membrane [1,2]. For enveloped viruses, such as human immunodeficiency virus type 1 (HIV-1) and influenza virus, oligomerization of the surface glycoproteins (gp) is featured in the envelope architecture and is essential for their function in viral entry and immunogenicity [3,4].…”

Section: Introductionmentioning

confidence: 99%

The application of perfluorooctanoate to investigate trimerization of the human immunodeficiency virus‐1 gp41 ectodomain by electrophoresis

et al. 2008

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The transmembrane glycoprotein gp41 of human immunodeficiency virus has been proposed to form trimer-of-hairpin during virus-cell membrane fusion. To investigate its oligomerization propensity under soluble and membrane-mimic conditions, sodium salt of perfluorooctanoate (PFO) was applied. A recombinant gp41 ectodomain devoid of disulfide linkage was overexpressed in Escherichia coli and characterized by MS and circular dichroism spectropolarimetry in PFO solution in comparison to SDS. The helical content of this ectodomain in PFO is higher than that in SDS. Notably, PFO employed in PAGE clearly conduced to the formation of trimer under the optimized condition as visualized in the gel. In addition, the proteins expressed from the two mutants in the heptad repeat (HR) domains of gp41, I62P, and N126K, were also examined by the PFO-PAGE analysis for functional ramification of molecular organization. Remarkably, the I62P mutation completely abolished the gp41 trimer formation, whereas the N126K mutation resulted in a more stable trimer. The data suggested that PFO-PAGE analysis is appropriate for evaluating the effect of mutations on the trimerization of gp41 and other fusion proteins which may be implicated in the alteration of their fusogenicity.

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Protein oligomerization: How and why

Cited by 319 publications

References 102 publications

Photoautotrophic Polyhydroxybutyrate Granule Formation Is Regulated by Cyanobacterial Phasin PhaP in Synechocystis sp. Strain PCC 6803

Photoautotrophic Polyhydroxybutyrate Granule Formation Is Regulated by Cyanobacterial Phasin PhaP in Synechocystis sp. Strain PCC 6803

Diversification of Paralogous α-Isopropylmalate Synthases by Modulation of Feedback Control and Hetero-Oligomerization in Saccharomyces cerevisiae

The application of perfluorooctanoate to investigate trimerization of the human immunodeficiency virus‐1 gp41 ectodomain by electrophoresis

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