Gayathri P, Banerjee Mousumi, Vijayalakshmi A, Azeez Shamina, Balaram Hemalatha, Balaram P, Murthy M R N
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
Acta Crystallogr D Biol Crystallogr. 2007 Feb;63(Pt 2):206-20. doi: 10.1107/S0907444906046488. Epub 2007 Jan 16.
The crystal structure of a recombinant triosephosphate isomerase (TIM) from the archaeabacterium Methanocaldococcus jannaschii has been determined at a resolution of 2.3 A using X-ray diffraction data from a tetartohedrally twinned crystal. M. jannaschii TIM (MjTIM) is tetrameric, as suggested by solution studies and from the crystal structure, as is the case for two other structurally characterized archaeal TIMs. The archaeabacterial TIMs are shorter compared with the dimeric TIMs; the insertions in the dimeric TIMs occur in the vicinity of the tetramer interface, resulting in a hindrance to tetramerization in the dimeric TIMs. The charge distribution on the surface of the archaeal TIMs also facilitates tetramerization. Analysis of the barrel interactions in TIMs suggests that these interactions are unlikely to account for the thermal stability of the archaeal TIMs. A novelty of the unliganded structure of MjTIM is the complete absence of electron density for the loop 6 residues. The disorder of this loop could be ascribed to a missing salt bridge between residues at the N- and C-terminal ends of the loop in MjTIM.
利用来自四面体孪晶的X射线衍射数据，已在2.3埃的分辨率下测定了来自嗜热栖热甲烷球菌的重组磷酸丙糖异构酶（TIM）的晶体结构。如溶液研究和晶体结构所表明的，嗜热栖热甲烷球菌TIM（MjTIM）是四聚体，另外两个已进行结构表征的古细菌TIM也是如此。与二聚体TIM相比，古细菌TIM更短；二聚体TIM中的插入片段出现在四聚体界面附近，导致二聚体TIM难以形成四聚体。古细菌TIM表面的电荷分布也有利于形成四聚体。对TIM中桶状结构相互作用的分析表明，这些相互作用不太可能解释古细菌TIM的热稳定性。MjTIM未结合配体结构的一个新奇之处在于，环6残基完全没有电子密度。该环的无序状态可能归因于MjTIM中环N端和C端残基之间缺少盐桥。
