The crystal structure of yeast thiamin pyrophosphokinase
The crystal structure of yeast thiamin pyrophosphokinase
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DOI：
10.1016/s0969-2126(01)00615-3
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发表时间：
2001-06-01
期刊：
影响因子：
5.7
通讯作者：
Timm, DE
中科院分区：
文献类型：
--
作者：
Baker, LJ;Dorocke, JA;Timm, DE
背景资料：硫胺素焦磷酸激酶（TPK）催化焦磷酸基团从ATP转移到维生素B-1（硫胺素）以形成辅酶焦磷酸硫胺素（TPP）。因此，TPK对于形成中枢代谢功能所需的辅酶是重要的。TPK在PDB中没有序列同源物，并且通过未知的机制起作用。TPK的结构已被确定为一个重要的步骤，阐明其催化action.Results：与硫胺素复合的酿酒酵母TPK的晶体结构已被确定在1.8埃分辨率，TPK是一个同源二聚体，每个亚基由两个结构域。一个结构域类似于Rossman折叠，在6链平行β折叠的每一侧具有四个α螺旋。另一个结构域具有一个4链和一个6链反平行β折叠，其形成含有卷曲拓扑结构的扁平夹层结构。活性位点位于二聚体界面处的裂缝中，并且由来自两个亚基的结构域的残基形成。TPK二聚体含有两个化合物的活性位点在亚基interfaces.Conclusions：TPK的结构与一个基板绑定的硫胺素结合位点和可能的催化残基的位置确定。该结构还表明可能存在ATP的结合位点。这些发现进一步得到TPK序列同源性的支持。虽然与其他焦磷酸激酶没有显著的序列同源性，但硫胺素焦磷酸激酶可能通过与核苷酸生物合成中的焦磷酸激酶功能相似的焦磷酸转移机制进行操作。
Background: Thiamin pyrophosphokinase (TPK) catalyzes the transfer of a pyrophosphate group from ATP to vitamin B-1 (thiamin) to form the coenzyme thiamin pyrophosphate (TPP). Thus, TPK is important for the formation of a coenzyme required for central metabolic functions. TPK has no sequence homologs in the PDB and functions by an unknown mechanism. The TPK structure has been determined as a significant step toward elucidating its catalytic action.Results: The crystal structure of Saccharomyces cerevisiae TPK complexed with thiamin has been determined at 1.8 Angstrom resolution, TPK is a homodimer, and each subunit consists of two domains. One domain resembles a Rossman fold with four alpha helices on each side of a 6 strand parallel beta sheet. The other domain has one 4 strand and one 6 strand antiparallel beta sheet, which form a flattened sandwich structure containing a jelly-roll topology. The active site is located in a cleft at the dimer interface and is formed from residues from domains of both subunits. The TPK dimer contains two compound active sites at the subunit interface.Conclusions: The structure of TPK with one substrate bound identifies the location of the thiamin binding site and probable catalytic residues. The structure also suggests a likely binding site for ATP. These findings are further supported by TPK sequence homologies. Although possessing no significant sequence homology with other pyrophospokinases, thiamin pyrophosphokinase may operate by a mechanism of pyrophosphoryl transfer similar to those described for pyrophosphokinases functioning in nucleotide biosynthesis.