Karuppiah Vijaykumar, Thistlethwaite Angela, Dajani Rana, Warwicker Jim, Derrick Jeremy P
From the Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, United Kingdom.
From the Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, United Kingdom
J Biol Chem. 2014 Nov 28;289(48):33187-97. doi: 10.1074/jbc.M114.608448. Epub 2014 Oct 13.
CinA is a widely distributed protein in Gram-positive and Gram-negative bacteria. It is associated with natural competence and is proposed to have a function as an enzyme participating in the pyridine nucleotide cycle, which recycles products formed by non-redox uses of NAD. Here we report the determination of the crystal structure of CinA from Thermus thermophilus, in complex with several ligands. CinA was shown to have both nicotinamide mononucleotide deamidase and ADP-ribose pyrophosphatase activities. The crystal structure shows an unusual asymmetric dimer, with three domains for each chain; the C-terminal domain harbors the nicotinamide mononucleotide deamidase activity, and the structure of a complex with the product nicotinate mononucleotide suggests a mechanism for deamidation. The N-terminal domain belongs to the COG1058 family and is associated with the ADP-ribose pyrophosphatase activity. The asymmetry in the CinA dimer arises from two alternative orientations of the COG1058 domains, only one of which forms a contact with the KH-type domain from the other chain, effectively closing the active site into, we propose, a catalytically competent state. Structures of complexes with Mg(2+)/ADP-ribose, Mg(2+)/ATP, and Mg(2+)/AMP suggest a mechanism for the ADP-ribose pyrophosphatase reaction that involves a rotation of the COG1058 domain dimer as part of the reaction cycle, so that each active site oscillates between open and closed forms, thus promoting catalysis.
CinA是一种在革兰氏阳性菌和革兰氏阴性菌中广泛分布的蛋白质。它与自然感受态相关，并且被认为具有作为参与吡啶核苷酸循环的酶的功能，该循环可回收由NAD的非氧化还原用途形成的产物。在此，我们报告了嗜热栖热菌CinA与几种配体复合物的晶体结构测定。结果表明，CinA具有烟酰胺单核苷酸脱酰胺酶和ADP - 核糖焦磷酸酶活性。晶体结构显示出一种不寻常的不对称二聚体，每条链有三个结构域；C末端结构域具有烟酰胺单核苷酸脱酰胺酶活性，与产物烟酸单核苷酸形成的复合物结构提示了脱酰胺作用的机制。N末端结构域属于COG1058家族，与ADP - 核糖焦磷酸酶活性相关。CinA二聚体中的不对称性源于COG1058结构域的两种交替取向，其中只有一种与另一条链的KH型结构域形成接触，有效地将活性位点封闭成我们提出的催化活性状态。与Mg(2+)/ADP - 核糖、Mg(2+)/ATP和Mg(2+)/AMP形成的复合物结构提示了ADP - 核糖焦磷酸酶反应的机制，该机制涉及COG1058结构域二聚体的旋转作为反应循环的一部分，使得每个活性位点在开放和封闭形式之间振荡，从而促进催化作用。
