Rich R L, Kreikemeyer B, Owens R T, LaBrenz S, Narayana S V, Weinstock G M, Murray B E, Höök M
Center for Extracellular Matrix Biology, Institute of Biosciences and Technology, Texas A&M University, Houston, Texas 77030, USA.
J Biol Chem. 1999 Sep 17;274(38):26939-45. doi: 10.1074/jbc.274.38.26939.
A putative collagen-binding MSCRAMM, Ace, of Enterococcus faecalis was identified by searching bacterial genome data bases for proteins containing domains homologous to the ligand-binding region of Cna, the collagen-binding MSCRAMM from Staphylococcus aureus. Ace was predicted to have a molecular mass of 71 kDa and contains features characteristic of cell surface proteins on Gram-positive bacteria, including a LPXTG motif for cross-linking to the cell wall. The N-terminal region of Ace contained a region (residues 174-319) in which 56% of the residues are identical or similar when compared with the minimal ligand-binding region of Cna (Cna 151-318); the remainder of the Ace A domain has 46% similarity with the corresponding region of the Cna A domain. Antibodies raised against recombinant Ace A domain were used to verify the cell surface expression of Ace on E. faecalis. These antibodies also effectively inhibited the adhesion of enterococcal cells to a collagen substrate, suggesting that Ace is a functional collagen-binding MSCRAMM. Structural modeling of the conserved region in Ace (residues 174-319) suggested a structure very similar to that reported for residues 151-318 of the Cna collagen-binding domain in which the ligand-binding site was identified as a trench transversing a beta-sheet face (Symersky, J., Patti, J. M., Carson, M., House-Pompeo, K., Teale, M., Moore, D., Jin, L., DeLucas, L. J., Höök, M., and Narayana, S. V. L. (1997) Nat. Struct. Biol. 10, 833-838). Biochemical analyses of recombinant Ace and Cna A domains supported the modeling data in that the secondary structures were similar as determined by CD spectroscopy and both proteins bound at multiple sites in type I collagen with micromolar affinities, but with different apparent kinetics. We conclude that Ace is a collagen-binding MSCRAMM on enterococci and is structurally and functionally related to the staphylococcal Cna protein.
通过在细菌基因组数据库中搜索含有与金黄色葡萄球菌的胶原结合微生物表面组分识别黏附分子（MSCRAMM）Cna的配体结合区域同源结构域的蛋白质，鉴定出一种粪肠球菌假定的胶原结合MSCRAMM，即Ace。预测Ace的分子量为71 kDa，并具有革兰氏阳性菌细胞表面蛋白的特征，包括用于与细胞壁交联的LPXTG基序。Ace的N端区域包含一个区域（第174 - 319位氨基酸残基），与Cna的最小配体结合区域（Cna 151 - 318）相比，该区域56%的氨基酸残基相同或相似；Ace A结构域的其余部分与Cna A结构域的相应区域有46%的相似性。针对重组Ace A结构域产生的抗体用于验证Ace在粪肠球菌上的细胞表面表达。这些抗体也有效抑制了肠球菌细胞与胶原底物的黏附，表明Ace是一种功能性的胶原结合MSCRAMM。Ace中保守区域（第174 - 319位氨基酸残基）的结构模型显示，其结构与报道的Cna胶原结合结构域第151 - 318位氨基酸残基的结构非常相似，其中配体结合位点被确定为横穿β折叠面的一条沟（Symersky, J., Patti, J. M., Carson, M., House-Pompeo, K., Teale, M., Moore, D., Jin, L., DeLucas, L. J., Höök, M., and Narayana, S. V. L. (1997) Nat. Struct. Biol. 10, 833 - 838）。重组Ace和Cna A结构域的生化分析支持了模型数据，即通过圆二色光谱法测定二级结构相似，且两种蛋白质都以微摩尔亲和力在I型胶原的多个位点结合，但表观动力学不同。我们得出结论，Ace是肠球菌上的一种胶原结合MSCRAMM，在结构和功能上与葡萄球菌的Cna蛋白相关。
