Luo Zhenyao, Morey Jacqueline R, McDevitt Christopher A, Kobe Boštjan
School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.
Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia.
Acta Crystallogr F Struct Biol Commun. 2015 Dec;71(Pt 12):1459-64. doi: 10.1107/S2053230X15021330. Epub 2015 Nov 18.
Zn(2+) is an essential nutrient for all known forms of life. In the major human pathogen Streptococcus pneumoniae, the acquisition of Zn(2+) is facilitated by two Zn(2+)-specific solute-binding proteins: AdcA and AdcAII. To date, there has been a paucity of structural information on AdcA, which has hindered a deeper understanding of the mechanism underlying pneumococcal Zn(2+) acquisition. Native AdcA consists of two domains: an N-terminal ZnuA domain and a C-terminal ZinT domain. In this study, the ZnuA domain of AdcA was crystallized. The initial crystals of the ZnuA-domain protein were obtained using dried seaweed as a heterogeneous nucleating agent. No crystals were obtained in the absence of the heterogeneous nucleating agent. These initial crystals were subsequently used as seeds to produce diffraction-quality crystals. The crystals diffracted to 2.03 Å resolution and had the symmetry of space group P1. This study demonstrates the utility of heterogeneous nucleation. The solution of the crystal structures will lead to further understanding of Zn(2+) acquisition by S. pneumoniae.
锌离子（Zn(2+)）是所有已知生命形式所必需的营养素。在主要的人类病原体肺炎链球菌中，两种锌离子特异性溶质结合蛋白AdcA和AdcAII促进了锌离子（Zn(2+)）的获取。迄今为止，关于AdcA的结构信息匮乏，这阻碍了对肺炎链球菌获取锌离子（Zn(2+)）机制的深入理解。天然的AdcA由两个结构域组成：一个N端的ZnuA结构域和一个C端的ZinT结构域。在本研究中，AdcA的ZnuA结构域被结晶。ZnuA结构域蛋白的初始晶体是使用干海藻作为异质成核剂获得的。在没有异质成核剂的情况下未获得晶体。这些初始晶体随后被用作晶种来生产具有衍射质量的晶体。这些晶体的衍射分辨率达到2.03 Å，具有空间群P1的对称性。本研究证明了异质成核的实用性。晶体结构的解析将有助于进一步了解肺炎链球菌对锌离子（Zn(2+)）的获取。
