Buchko Garry W, Yee Adelinda, Semesi Anthony, Myler Peter J, Arrowsmith Cheryl H, Hui Raymond
Seattle Structural Genomics Center for Infectious Disease, USA.
Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
Acta Crystallogr F Struct Biol Commun. 2015 May;71(Pt 5):514-21. doi: 10.1107/S2053230X1402799X. Epub 2015 Apr 18.
Protozoa of the genus Plasmodium are responsible for malaria, which is perhaps the most important parasitic disease to infect mankind. The emergence of Plasmodium strains resistant to current therapeutics and prophylactics makes the development of new treatment strategies urgent. Among the potential targets for new antimalarial drugs is the BolA-like protein PFE0790c from Plasmodium falciparum (Pf-BolA). While the function of BolA is unknown, it has been linked to cell morphology by regulating transcription in response to stress. Using an NMR-based method, an ensemble of 20 structures of Pf-BolA was determined and deposited in the PDB (PDB entry 2kdn). The overall topology of the Pf-BolA structure, α1-β1-β2-η1-α2/η2-β3-α3, with the β-strands forming a mixed β-sheet, is similar to the fold observed in other BolA structures. A helix-turn-helix motif similar to the class II KH fold associated with nucleic acid-binding proteins is present, but contains an FXGXXXL signature sequence that differs from the GXXG signature sequence present in class II KH folds, suggesting that the BolA family of proteins may use a novel protein-nucleic acid interface. A well conserved arginine residue, Arg50, hypothesized to play a role in governing the formation of the C-terminal α-helix in the BolA family of proteins, is too distant to form polar contacts with any side chains in this α-helix in Pf-BolA, suggesting that this conserved arginine may only serve a role in guiding the orientation of this C-terminal helix in some BolA proteins. A survey of BolA structures suggests that the C-terminal helix may not have a functional role and that the third helix (α2/η2) has a `kink' that appears to be conserved among the BolA protein structures. Circular dichroism spectroscopy shows that Pf-BolA is fairly robust, partially unfolding when heated to 353 K and refolding upon cooling to 298 K.
疟原虫属的原生动物是导致疟疾的病原体，疟疾可能是感染人类的最重要的寄生虫病。对当前治疗药物和预防药物产生耐药性的疟原虫菌株的出现，使得开发新的治疗策略变得紧迫。新型抗疟药物的潜在靶点之一是恶性疟原虫的BolA样蛋白PFE0790c（Pf-BolA）。虽然BolA的功能尚不清楚，但它已被认为通过在应激反应中调节转录而与细胞形态相关。使用基于核磁共振的方法，确定了Pf-BolA的20种结构的集合，并将其存入蛋白质数据库（PDB登录号2kdn）。Pf-BolA结构的总体拓扑结构为α1-β1-β2-η1-α2/η2-β3-α3，其中β链形成混合β折叠，与在其他BolA结构中观察到的折叠相似。存在一个类似于与核酸结合蛋白相关的II类KH折叠的螺旋-转角-螺旋基序，但包含一个FXGXXXL特征序列，该序列不同于II类KH折叠中存在的GXXG特征序列，这表明BolA蛋白家族可能使用一种新型的蛋白质-核酸界面。一个保守的精氨酸残基Arg50，据推测在BolA蛋白家族中C端α螺旋的形成中起作用，但在Pf-BolA中，它距离该α螺旋中的任何侧链都太远，无法形成极性接触，这表明这个保守的精氨酸可能仅在某些BolA蛋白中指导该C端螺旋的方向。对BolA结构的研究表明，C端螺旋可能没有功能作用，并且第三个螺旋（α2/η2）有一个“扭结”，这在BolA蛋白结构中似乎是保守的。圆二色光谱表明Pf-BolA相当稳定，加热到353 K时部分展开，冷却到298 K时重新折叠。
