University of North Carolina-Chapel Hill, Dept. of Chemistry, Chapel Hill, NC 27599-3290, USA.
J Bacteriol. 2011 May;193(9):2089-96. doi: 10.1128/JB.01231-10. Epub 2011 Mar 11.
The heparin-binding hemagglutinin adhesin (HBHA) is a surface adhesin on the human pathogen Mycobacterium tuberculosis. Previously, it has been shown that HBHA exists as a dimer in solution. We investigated the detailed nature of this dimer using circular dichroism spectroscopy and analytical ultracentrifugation techniques. We demonstrate that the heparan sulfate (HS) binding region does not play a role in dimerization in solution, while the linker region between the predicted N-terminal coiled-coil and the C-terminal HS binding region does affect dimer stability. The majority of contacts responsible for dimerization, folding, and stability lie within the predicted coiled-coil region of HBHA, while the N-terminal helix preceding the coiled-coil appears to trigger the folding and dimerization of HBHA. Constructs lacking this initial helix or containing site-specific mutations produce nonhelical monomers in solution. Thus, we show that HBHA dimerization and folding are linked and that the N-terminal region of this cell surface adhesin triggers the formation of an HBHA coiled-coil dimer.
肝素结合血凝素黏附素（HBHA）是人类病原体结核分枝杆菌表面黏附素。先前的研究表明，HBHA 以二聚体的形式存在于溶液中。我们使用圆二色性光谱法和分析超速离心技术研究了这种二聚体的详细性质。我们证明，硫酸乙酰肝素（HS）结合区在溶液中二聚化过程中不起作用，而在预测的 N 端卷曲螺旋和 C 端 HS 结合区之间的连接区确实影响二聚体稳定性。负责二聚化、折叠和稳定性的大部分接触都位于 HBHA 的预测卷曲螺旋区，而卷曲螺旋之前的 N 端螺旋似乎触发了 HBHA 的折叠和二聚化。缺乏此初始螺旋的构建体或包含特定部位突变的构建体在溶液中产生无规卷曲的单体。因此，我们表明 HBHA 的二聚化和折叠是相关的，并且该细胞表面黏附素的 N 端区域触发了 HBHA 卷曲螺旋二聚体的形成。
