Krebs Institute, School of Biosciences, University of Sheffield, Sheffield, S10 2TN, UK.
Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA, 91125, USA.
Commun Biol. 2022 Mar 28;5(1):272. doi: 10.1038/s42003-022-03186-2.
Burkholderia pseudomallei lethal factor 1 (BLF1) exhibits site-specific glutamine deamidase activity against the eukaryotic RNA helicase, eIF4A, thereby blocking mammalian protein synthesis. The structure of a complex between BLF1 C94S and human eIF4A shows that the toxin binds in the cleft between the two RecA-like eIF4A domains forming interactions with residues from both and with the scissile amide of the target glutamine, Gln339, adjacent to the toxin active site. The RecA-like domains adopt a radically twisted orientation compared to other eIF4A structures and the nature and position of conserved residues suggests this may represent a conformation associated with RNA binding. Comparison of the catalytic site of BLF1 with other deamidases and cysteine proteases reveals that they fall into two classes, related by pseudosymmetry, that present either the re or si faces of the target amide/peptide to the nucleophilic sulfur, highlighting constraints in the convergent evolution of their Cys-His active sites.
类鼻疽伯克霍尔德菌致死因子 1（BLF1）对真核 RNA 解旋酶 eIF4A 具有位点特异性谷氨酰胺脱氨酶活性，从而阻断哺乳动物蛋白质合成。BLF1 C94S 与人 eIF4A 之间形成的复合物结构表明，该毒素结合在两个 RecA 样 eIF4A 结构域之间的裂隙中，与两个结构域的残基形成相互作用，并与靶谷氨酸 Gln339 的酰胺键形成相互作用，Gln339 位于毒素活性位点的附近。与其他 eIF4A 结构相比，RecA 样结构域采用了一种完全扭曲的取向，保守残基的性质和位置表明这可能代表一种与 RNA 结合相关的构象。BLF1 的催化位点与其他脱酰胺酶和半胱氨酸蛋白酶的比较表明，它们属于两类，通过拟对称关系相关，将靶酰胺/肽的 re 或 si 面呈现给亲核硫原子，突出了它们 Cys-His 活性位点趋同进化的约束。
