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Acta Crystallographica Section F: Structural Biology and Crystallization Communications (1)
Frontiers in Microbiology (1)
Journal of Bacteriology (1)
Archer, Margarida (3)
Borges, Nuno (2)
Brito, José A. (2)
Santos, Helena (2)
Afonso, José P. (1)
Franklin, Edward (1)
Khan, Amir R. (1)
Oldham, Neil J. (1)
Oliveira, Tânia F. (1)
Pereira, Inês A. C. (1)
Vonrhein, Clemens (1)
Year of Publication
Production, crystallization and preliminary X-ray analysis of CTP:inositol-1-phosphate cytidylyltransferase from Archaeoglobus fulgidus
Brito, José A.
Acta Crystallographica Section F: Structural Biology and Crystallization Communications
The expression, purification, crystallization and preliminary X-ray diffraction analysis of CTP:inositol-1-phosphate cytidylyltransferase from A. fulgidus is described.
Archaeoglobus fulgidus, a hyperthermophilic archaeon, accumulates di-myo-inositol phosphate (DIP) in response to heat stress. Recently, the pathway for biosynthesis of DIP has been elucidated in this organism and involves a bifunctional enzyme that contains two domains: CTP:inositol-1-phosphate cytidylyltransferase (IPCT) as a soluble domain and di-myo-inositol-1,3′-phosphate-1-phosphate synthase (DIPPS) as a membrane domain. Here, the expression, purification, crystallization and preliminary X-ray diffraction analysis of the IPCT domain from A. fulgidus in the apo form are reported. The crystals diffracted to 2.4 Å resolution using a synchrotron source and belonged to the orthorhombic space group P21212, with unit-cell parameters a = 154.7, b = 83.9, c = 127.7 Å.
CTP:inositol-1-phosphate cytidylyltransferase; Archaeoglobus fulgidus; compatible solutes; CDP-inositol; di-myo-inositol phosphate
Crystal Structure of Archaeoglobus fulgidus CTP:Inositol-1-Phosphate Cytidylyltransferase, a Key Enzyme for Di-myo-Inositol-Phosphate Synthesis in (Hyper)Thermophiles▿†
Brito, José A.
Journal of Bacteriology
Many Archaea and Bacteria isolated from hot, marine environments accumulate di-myo-inositol-phosphate (DIP), primarily in response to heat stress. The biosynthesis of this compatible solute involves the activation of inositol to CDP-inositol via the action of a recently discovered CTP:inositol-1-phosphate cytidylyltransferase (IPCT) activity. In most cases, IPCT is part of a bifunctional enzyme comprising two domains: a cytoplasmic domain with IPCT activity and a membrane domain catalyzing the synthesis of di-myo-inositol-1,3′-phosphate-1′-phosphate from CDP-inositol and l-myo-inositol phosphate. Herein, we describe the first X-ray structure of the IPCT domain of the bifunctional enzyme from the hyperthermophilic archaeon Archaeoglobus fulgidus DSMZ 7324. The structure of the enzyme in the apo form was solved to a 1.9-Å resolution. The enzyme exhibited apparent Km values of 0.9 and 0.6 mM for inositol-1-phosphate and CTP, respectively. The optimal temperature for catalysis was in the range 90 to 95°C, and the Vmax determined at 90°C was 62.9 μmol · min−1 · mg of protein−1. The structure of IPCT is composed of a central seven-stranded mixed β-sheet, of which six β-strands are parallel, surrounded by six α-helices, a fold reminiscent of the dinucleotide-binding Rossmann fold. The enzyme shares structural homology with other pyrophosphorylases showing the canonical motif G-X-G-T-(R/S)-X4-P-K. CTP, l-myo-inositol-1-phosphate, and CDP-inositol were docked into the catalytic site, which provided insights into the binding mode and high specificity of the enzyme for CTP. This work is an important step toward the final goal of understanding the full catalytic route for DIP synthesis in the native, bifunctional enzyme.
Structural Insights into Dissimilatory Sulfite Reductases: Structure of Desulforubidin from Desulfomicrobium Norvegicum
Oliveira, Tânia F.
Afonso, José P.
Khan, Amir R.
Oldham, Neil J.
Pereira, Inês A. C.
Frontiers in Microbiology
Dissimilatory sulfite reductases (dSiRs) are crucial enzymes in bacterial sulfur-based energy metabolism, which are likely to have been present in some of the earliest life forms on Earth. Several classes of dSiRs have been proposed on the basis of different biochemical and spectroscopic properties, but it is not clear whether this corresponds to actual physiological or structural differences. Here, we describe the first structure of a dSiR from the desulforubidin class isolated from Desulfomicrobium norvegicum. The desulforubidin (Drub) structure is assembled as α2β2γ2, in which two DsrC proteins are bound to the core [DsrA]2[DsrB]2 unit, as reported for the desulfoviridin (Dvir) structure from Desulfovibrio vulgaris. Unlike Dvir, four sirohemes and eight [4Fe–4S] clusters are present in Drub. However, the structure indicates that only two of the Drub coupled siroheme-[4Fe–4S] cofactors are catalytically active. Mass spectrometry studies of purified Drub and Dvir show that both proteins present different oligomeric complex forms that bind two, one, or no DsrC proteins, providing an explanation for conflicting spectroscopic and biochemical results in the literature, and further indicating that DsrC is not a subunit of dSiR, but rather a protein with which it interacts.
sulfite reductases; sulfur metabolism; sulfate reducing bacteria; siroheme; iron–sulfur clusters; X-ray structure
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