Hyaluronan Binding to Link Module of TSG-6 and to G1 Domain of Aggrecan Is Differently Regulated by pH
Hyaluronan Binding to Link Module of TSG-6 and to G1 Domain of Aggrecan Is Differently Regulated by pH
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DOI：
10.1074/jbc.m804155200
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发表时间：
2008-11-21
影响因子：
4.8
通讯作者：
Hardingham, Timothy E.
中科院分区：
文献类型：
--
作者：
Heng, Boon Chin;Gribbon, Philip M.;Hardingham, Timothy E.
透明质酸（HA）在脊椎动物组织细胞外基质中的生理功能涉及一系列特异性蛋白质相互作用。在这项研究中，HA与连接模块从TSG-6（Link_TSG 6）和聚集蛋白聚糖的G1域（G1）的相互作用，研究了在稀溶液中的翻译扩散的生物物理分析，使用共聚焦荧光恢复后光漂白（共聚焦FRAP）。Link_TSG6和G1均显示与聚合HA结合，并且这些相互作用可分别与HA（8）和HA（10）寡糖竞争。平衡实验表明，Link_TSG6与HA的结合亲和力在pH 6.0时最大，高于和低于该pH时显著降低。相反，G1在pH 7.0-8.0时具有最大结合，在更宽的pH范围（5.5-8.0）内具有中等至强的结合亲和力。对于Link_TSG6与HA结合所确定的K-D显示在pH 7.4和6.0之间结合亲和力增加100倍，而G1显示在相同pH范围内结合亲和力降低75倍。在它们的pH结合中观察到的显著差异表明pH控制TSG-6的生理功能，在中性pH下对HA具有低亲和力，但当pH福尔斯降至pH 7以下时具有增加的亲和力。TSG-6和聚集蛋白聚糖通过结构上同源的结构域与HA相互作用，pH依赖性结合的差异可以根据Link_TSG 6中关键调控氨基酸的存在和拓扑分布以及聚集蛋白聚糖G1中相关串联Link结构域的差异来理解。
The physiological functions of hyaluronan (HA) in the extracellular matrix of vertebrate tissues involve a range of specific protein interactions. In this study, the interaction of HA with the Link module from TSG-6 (Link_TSG6) and G1 domain of aggrecan (G1), were investigated by a biophysical analysis of translational diffusion in dilute solution using confocal fluorescence recovery after photobleaching (confocal FRAP). Both Link_TSG6 and G1 were shown to bind to polymeric HA and these interactions could be competed with HA(8) and HA(10) oligosaccharides, respectively. Equilibrium experiments showed that the binding affinity of Link_TSG6 to HA was maximal at pH 6.0, and reduced dramatically above and below this pH. In contrast, G1 had maximum binding at pH 7.0-8.0 and moderate to strong binding affinity over a much broader pH range (5.5-8.0). The K-D determined for Link_TSG6 binding to HA showed a 100-fold increase in binding affinity between pH 7.4 and 6.0, whereas G1 showed a 75-fold decrease in binding affinity over the same pH range. The sharp difference observed in their pH binding suggests that pH controls the physiological function of TSG-6, with a low affinity for HA at neutral pH, but with increased affinity as the pH falls below pH 7. TSG-6 and aggrecan interact with HA through structurally homologous domains and the difference in pH-dependent binding can be understood in terms of differences in the presence and topographical distribution of key regulatory amino acids in Link_TSG6 and in the related tandem Link domains in aggrecan G1.