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Structural and Functional Characterization of Plasmodium falciparum Nicotinic Acid Mononucleotide Adenylyltransferase

机译:恶性疟原虫烟酸单核苷酸腺苷酸转移酶的结构和功能表征

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Nicotinic acid mononucleotide adenylyltransferase (NaMNAT) is an indispensable enzyme for the synthesis of NAD and NAD phosphate. It catalyzes the adenylylation of nicotinic acid mononucleotide (NaMN) to yield nicotinic acid adenine dinucleotide (NaAD). Since NAD(H) and NAD phosphate(H) are essentially involved in metabolic and redox regulatory reactions, NaMNAT is an attractive drug target in the fight against bacterial and parasitic infections. Notably, NaMNAT of the malaria parasite Plasmodium falciparum possesses only 20% sequence identity with the homologous human enzyme. Here, we present for the first time the two X-ray structures of P. falciparum NaMNAT (PfNaMNAT)-in the product-bound state with NaAD and. complexed with an alpha,beta-non-hydrolizable ATP analog the structures were determined to a resolution of 2.2 angstrom and 2.5 angstrom, respectively. The overall architecture of PfNaMNAT was found to be more similar to its bacterial homologs than its human counterparts although the PPHK motif conserved in bacteria is missing. Furthermore, PfNaMNAT possesses two cysteine residues within the active site that have not been described for any other NaMNATase so far and are likely to be involved in redox regulation of PfNaMNAT activity. Enzymatic studies and surface plasmon resonance data reveal that PfNaMNAT is capable of utilizing NaMN and nicotinamide mononucleotide with a slight preference for NaMN. Surprisingly, a comparison with the active site of Escherichia coli NaMNAT showed very similar architectures, despite different substrate preferences. (C) 2016 Elsevier Ltd. All rights reserved.
机译:烟酸单核苷酸腺苷酸转移酶(NaMNAT)是合成NAD和NAD磷酸必不可少的酶。它催化烟酸单核苷酸(NaMN)的腺苷酸化反应,产生烟酸腺嘌呤二核苷酸(NaAD)。由于NAD(H)和NAD磷酸盐(H)基本上参与代谢和氧化还原调节反应,因此NaMNAT在对抗细菌和寄生虫感染方面是有吸引力的药物靶标。值得注意的是,疟原虫恶性疟原虫的NaMNAT与同源人类酶仅具有20%的序列同一性。在这里,我们首次展示了恶性疟原虫NaMNAT(PfNaMNAT)的两个X射线结构,它们与NaAD和呈结合状态。与α,β-不可水解的ATP类似物复合,确定结构的分辨率分别为2.2埃和2.5埃。尽管缺少在细菌中保守的PPHK基序,但发现PfNaMNAT的总体结构与其人类同源基因更相似于其细菌同源物。此外,PfNaMNAT在活性位点中具有两个半胱氨酸残基,到目前为止尚无其他NaMNATase的描述,并且可能参与PfNaMNAT活性的氧化还原调节。酶学研究和表面等离振子共振数据表明,PfNaMNAT能够利用NaMN和烟酰胺单核苷酸,但对NaMN略有偏爱。令人惊讶地,与大肠杆菌NaMNAT的活性位点的比较显示了非常相似的结构,尽管底物偏好不同。 (C)2016 Elsevier Ltd.保留所有权利。

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