NADP(+)-dependent isocitrate dehydrogenase from Yarrowia lipolytica CLIB122 (YlIDP) was overexpressed and purified. The molecular mass of YlIDP was estimated to be about 81.3 kDa, suggesting its homodimeric structure in solution. YlIDP was divalent cation dependent and Mg(2+) was found to be the most favorable cofactor. The purified recombinant YlIDP displayed maximal activity at 55 °C and its optimal pH for catalysis was found to be around 8.5. Heat inactivation studies revealed that the recombinant YlIDP was stable below 45 °C, but its activity dropped quickly above this temperature. YlIDP was absolutely dependent on NADP(+) and no NAD-dependent activity could be detected. The K m values displayed for NADP(+) and isocitrate were 59 and 31 μM (Mg(2+)), 120 μM and 58 μM (Mn(2+)), respectively. Mutant enzymes were constructed to tentatively alter the coenzyme specificity of YlIDP. The K m values for NADP(+) of R322D mutant was 2,410 μM, being about 41-fold higher than that of wild type enzyme. NAD(+)-dependent activity was detected for R322D mutant and the K m and k cat values for NAD(+) were 47,000 μM and 0.38 s(-1), respectively. Although the R322D mutant showed low activity with NAD(+), it revealed the feasibility of engineering an eukaryotic IDP to a NAD(+)-dependent one.

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According to morphological and molecular data, a new species of Lecidea s. str., Lecidea glacierensis, is described from Xinjiang Province, China. It is distinctive due to its well-developed, regularly areolate to bullate thallus, and its habitat on calciferous rocks. This species was collected mostly in the area of Tianshan No.1 Glacier, which is located at an elevation of 3454 m and c. 118 km south-west of Urumqi and is considered to be one of the most important dryland glacier areas in Asia. An illustration and detailed description of the taxon are provided.

No abstract

A 10.5 kDa non-Pfam hypothetical protein, AF1514, from the hyperthermophilic archaeon Archeoglobus fulgidus has been overexpressed in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. The crystals diffracted X-rays to 2.09 Å resolution and a data set was collected at 100 K using Cu K radiation from a rotating-anode X-ray source. The crystals belong to space group P4 1 2 1 2 or P4 3 2 1 2, with unit-cell parameters a = b = 49.27, c = 106.61 Å . The calculated Matthews coefficient was 3.16 Å 3 Da À1, suggesting the presence of one molecule in the asymmetric unit.