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The crystal structures of the -crystalline-like soluble quinone oxidoreductase from Thermus thermophilus HB8 (QOR Tt ) and of its complex with NADPH have been determined at 2.3-and 2.8-Å resolutions, respectively. QOR Tt is composed of two domains, and its overall fold is similar to the folds of Escherichia coli quinone oxidoreductase (QOR Ec ) and horse liver alcohol dehydrogenase. QOR Tt forms a homodimer in the crystal by interaction of the ␤F-strands in domain II, forming a large ␤-sheet that crosses the dimer interface. High thermostability of QOR Tt was evidenced by circular dichroic measurement. NADPH is located between the two domains in the QOR Tt -NADPH complex. The disordered segment involved in the coenzyme binding of apo-QOR Tt becomes ordered upon NADPH binding. The segment covers an NADPH-binding cleft and may serve as a lid. The 2-phosphate group of the adenine of NADPH is surrounded by polar and positively charged residues in QOR Tt , suggesting that QOR Tt binds NADPH more readily than NADH. The putative substratebinding site of QOR Tt , unlike that of QOR Ec , is largely blocked by nearby residues, permitting access only to small substrates. This may explain why QOR Tt has weak p-benzoquinone reduction activity and is inactive with such large substrates of QOR Ec as 5-hydroxy-1,4-naphthoquinone and phenanthraquinone.

IscU plays a key role during iron-sulphur (Fe-S) cluster biosynthesis as a scaffold for the assembly of a nascent, highly labile Fe-S cluster. Here we report the characterization of an IscU-type protein (Aa IscU) from the hyperthermophilic bacterium Aquifex aeolicus. Unlike other known homologues of IscU, expression of Aa IscU in Escherichia coli has yielded an Fe-S cluster-containing holo-protein. Biochemical and spectroscopic studies of the wild-type Aa IscU and its Asp38-to-Ala substituted (D38A) variant molecule indicate that the holo-protein forms a trimer containing substoichiometric [2Fe-2S] cluster with its stability substantially increased by a D38A substitution. The [2Fe-2S] cluster was oxygen-labile and upon loss of the cluster, the resultant apo-form dissociated into a smaller species, a mixture of monomer and dimer with the dimer form predominating. Reddish-brown crystals of holo-Aa IscU-D38A were obtained under anaerobic conditions, that gave diffractions beyond 2.0 A resolution with synchrotron radiation. The crystal belongs to the space group P2(1)2(1)2 with unit-cell parameters a = 72.6, b = 122.3, c = 62.4 A, where the asymmetric unit contains three molecules of Aa IscU. Successful crystallization of holo-Aa IscU-D38A strongly suggests that the trimer association carrying substoichiometric [2Fe-2S] cluster represents a conformationally stable oligomeric state.

Primary graft failure can be a cause of early morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT), as it leads to a high risk of severe infections and bleeding. Splenomegaly is associated with primary graft failure in patients of myelofibrosis, but the association between splenomegaly and outcomes after HSCT in patients with myeloid malignancies has not been previously evaluated. The aim of this study was to investigate the effect of spleen volume on engraftment kinetics in patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We enrolled 85 patients. The median spleen volume was 146 cm (quartile 88-201 cm). The adjusted hazard ratios for neutrophil and platelet engraftments were 0.17 (0.07-0.40, p < 0.001) and 0.19 (0.05-0.69, p = 0.011), respectively, for the high-risk group, at a cutoff splenic volume of 320 cm. Overall survival at 3 years after HSCT was significantly poor in the high-risk group with an adjusted hazard ratio of 13.8 (2.61-72.4, p = 0.002). Enlarged spleen was associated with low neutrophil and platelet engraftment rates and poor survival after allogeneic HSCT in patients of AML and MDS.

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