Chi Ying-Chih, Rahkola Jeremy T, Kendrick Agnieszka A, Holliday Michael J, Paukovich Natasia, Roberts Thomas S, Janoff Edward N, Eisenmesser Elan Z
Departments of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, CO.
Mucosal and Vaccine Research Program Colorado (MAVRC), University of Colorado Denver, Aurora, CO.
Protein Sci. 2017 Mar;26(3):600-610. doi: 10.1002/pro.3110. Epub 2017 Feb 23.
IgA1 proteases (IgA1P) from diverse pathogenic bacteria specifically cleave human immunoglobulin A1 (IgA1) at the hinge region, thereby thwarting protective host immune responses. Streptococcus pneumoniae (S. pneumoniae) IgA1P shares no sequence conservation with serine or cysteine types of IgA1Ps or other known proteins, other than a conserved HExxH Zn-binding motif (1604-1608) found in metalloproteases. We have developed a novel expression system to produce the mature S. pneumoniae IgA1P and we have discovered that this form is both attached to the bacterial cell surface and released in its full form. Our data demonstrate that the S. pneumoniae IgA1P comprises two distinct regions that associate to form an active metalloprotease, the first such example of a metalloprotease that can be split in vitro and recombined to form an active enzyme. By capitalizing on this novel domain architecture, we show that the N-terminal region of S. pneumoniae IgA1P comprises the primary binding region for IgA1, although the C-terminal region of S. pneumoniae IgA1P is necessary for cleavage of IgA1. Our findings lend insight into the protein domain architecture of the S. pneumoniae IgA1P and function of this important virulence factor for S. pneumoniae infection.
来自多种致病细菌的IgA1蛋白酶（IgA1P）可在铰链区特异性切割人免疫球蛋白A1（IgA1），从而阻碍宿主的保护性免疫反应。肺炎链球菌（S. pneumoniae）的IgA1P与丝氨酸或半胱氨酸类型的IgA1P或其他已知蛋白质没有序列保守性，除了在金属蛋白酶中发现的保守的HExxH锌结合基序（1604 - 1608）。我们开发了一种新型表达系统来生产成熟的肺炎链球菌IgA1P，并且我们发现这种形式既附着在细菌细胞表面，又以完整形式释放。我们的数据表明，肺炎链球菌IgA1P由两个不同的区域组成，它们结合形成一种活性金属蛋白酶，这是金属蛋白酶中第一个可以在体外拆分并重新组合形成活性酶的例子。通过利用这种新型结构域架构，我们表明肺炎链球菌IgA1P的N端区域包含IgA1的主要结合区域，尽管肺炎链球菌IgA1P的C端区域对于IgA1的切割是必需的。我们的发现有助于深入了解肺炎链球菌IgA1P的蛋白质结构域架构以及这种肺炎链球菌感染重要毒力因子的功能。
