Safo Martin K, Musayev Faik N, di Salvo Martino L, Hunt Sharyn, Claude Jean-Baptiste, Schirch Verne
Department of Medicinal Chemistry and Institute for Structural Biology and Drug Discovery, 800 E. Leigh St., Virginia Commonwealth University, Richmond, VA 23219, USA.
J Bacteriol. 2006 Jun;188(12):4542-52. doi: 10.1128/JB.00122-06.
The pdxK and pdxY genes have been found to code for pyridoxal kinases, enzymes involved in the pyridoxal phosphate salvage pathway. Two pyridoxal kinase structures have recently been published, including Escherichia coli pyridoxal kinase 2 (ePL kinase 2) and sheep pyridoxal kinase, products of the pdxY and pdxK genes, respectively. We now report the crystal structure of E. coli pyridoxal kinase 1 (ePL kinase 1), encoded by a pdxK gene, and an isoform of ePL kinase 2. The structures were determined in the unliganded and binary complexes with either MgATP or pyridoxal to 2.1-, 2.6-, and 3.2-A resolutions, respectively. The active site of ePL kinase 1 does not show significant conformational change upon binding of either pyridoxal or MgATP. Like sheep PL kinase, ePL kinase 1 exhibits a sequential random mechanism. Unlike sheep pyridoxal kinase, ePL kinase 1 may not tolerate wide variation in the size and chemical nature of the 4' substituent on the substrate. This is the result of differences in a key residue at position 59 on a loop (loop II) that partially forms the active site. Residue 59, which is His in ePL kinase 1, interacts with the formyl group at C-4' of pyridoxal and may also determine if residues from another loop (loop I) can fill the active site in the absence of the substrate. Both loop I and loop II are suggested to play significant roles in the functions of PL kinases.
已发现pdxK和pdxY基因编码吡哆醛激酶，这些酶参与磷酸吡哆醛补救途径。最近发表了两种吡哆醛激酶结构，分别是大肠杆菌吡哆醛激酶2（ePL激酶2）和绵羊吡哆醛激酶，它们分别是pdxY和pdxK基因的产物。我们现在报告由pdxK基因编码的大肠杆菌吡哆醛激酶1（ePL激酶1）以及ePL激酶2的一种同工型的晶体结构。这些结构分别在与MgATP或吡哆醛形成的未结合和二元复合物中确定，分辨率分别为2.1 Å、2.6 Å和3.2 Å。ePL激酶1的活性位点在结合吡哆醛或MgATP后未显示出明显的构象变化。与绵羊PL激酶一样，ePL激酶1表现出顺序随机机制。与绵羊吡哆醛激酶不同，ePL激酶1可能无法容忍底物上4'取代基在大小和化学性质上的广泛变化。这是由于在部分形成活性位点的一个环（环II）上第59位的一个关键残基存在差异所致。在ePL激酶1中为His的第59位残基与吡哆醛C-4'处的甲酰基相互作用，并且还可能决定在没有底物的情况下另一个环（环I）的残基是否能够填充活性位点。环I和环II都被认为在PL激酶的功能中起重要作用。
