盐酸胍诱导八肋游仆虫中心蛋白与XPC肽复合物的解折叠

Unfolding of Euplotes octocarinatus centrin-xeroderma pigmentosum group C protein (XPC) peptide complex induced by guanidine hydrochloride

为探索真核生物核苷酸切除修复的可能性,选择人着色性干皮病(XPC)包含中心蛋白结合的多肽为研究对象,采用圆二色谱(CD)、荧光光谱与等温滴定量热法(ITC)对八肋游仆虫中心蛋白(EoCen)的靶肽结合进行了构象与热力学表征.结果表明C端结构域是XPC结合的关键位点,XPC发生构象变化由无规则状态转变为α-螺旋,色氨酸残基镶嵌在C端EF-手形成的疏水腔中,靶肽识别是放热反应,焓变对吉布斯自由能的贡献很大.盐酸胍诱导EoCen-XPC复合物的解折叠机理,并不是使复合物解离,而是使容纳XPC的C端疏水腔瓦解,XPC游离出来.

To explore the possibility of nucleotide excision repair in the eucaryotic organism,we chose a peptide from human xeroderma pigmentosum group C protein(XPC)covering the pivotal centrinbinding region and investigated the conformation and thermodynamic properties of target peptide binding of Euplotes octocarinatus centrin(EoCen)by circular dichroism(CD),fluorescence spectra and isothermal titration calorimetry(ITC).The C-terminal domain was the crucial region that anchored XPC,and XPC underwent conformational transition from a random coil toα-helix.The tryptophan residue of peptide was oriented in the hydrophobic channel formed by C-terminal EF-hand motifs,and peptide recognition of EoCen was exothermic reaction.Enthalpy change contributed to Gibbs free energy greatly.The unfolding mechanism of EoCen-XPC induced by guanidine hydrochloride was not dissociation of complex,but that the hydrophobic channel that hold XPC peptide was collapsed,and XPC peptide was released.