Environmentally induced reversible conformational switching in the yeast cell adhesion protein alpha-agglutinin.
Environmentally induced reversible conformational switching in the yeast cell adhesion protein alpha-agglutinin.
复制标题
环境诱导酵母细胞粘附蛋白α-凝集素的可逆构象转换。
DOI：
10.1110/ps.41701
复制
发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Lipke,PN
中科院分区：
文献类型：
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作者：
Zhao,H;Chen,MH;Shen,ZM;Kahn,PC;Lipke,PN
酵母细胞粘附蛋白 α-凝集素在自由生活的生物体表面表达，并受到各种环境条件的影响。圆二色性 (CD) 光谱显示 α-凝集素的结合区域具有富含 β-折叠的结构，在天然条件下（15-40°C，pH 5.5）仅含有约 2% 的 α-螺旋。该区域预计会折叠成三个免疫球蛋白样结构域，并且模型与 CD 谱以及肽图谱和位点特异性诱变一致。然而，二级结构预测算法表明，包含约 17% 残基的片段具有高 α 螺旋和低 β 折叠潜力。这些片段的两种模型肽具有螺旋倾向，其中一种肽表现出 pH 依赖性构象转换。同样，α-凝集素结合区域的 CD 光谱显示，在高温或 pH 值变化时，从富含 β 的结构可逆地转变为混合 α/β 结构。这些变化的可逆性意味着全β态和α/β态之间存在很小的能量差异。肽或二硫键断裂后也发生类似的变化。总之，这些观察结果表明，高螺旋倾向的短序列在天然条件下通过共价和局部电荷相互作用被限制为富β状态，但在非天然条件下形成螺旋。
The yeast cell adhesion protein α‐agglutinin is expressed on the surface of a free‐living organism and is subjected to a variety of environmental conditions. Circular dichroism (CD) spectroscopy shows that the binding region of α‐agglutinin has a β‐sheet‐rich structure, with only ∼2% α‐helix under native conditions (15–40°C at pH 5.5). This region is predicted to fold into three immunoglobulin‐like domains, and models are consistent with the CD spectra as well as with peptide mapping and site‐specific mutagenesis. However, secondary structure prediction algorithms show that segments comprising ∼17% of the residues have high α‐helical and low β‐sheet potential. Two model peptides of such segments had helical tendencies, and one of these peptides showed pH‐dependent conformational switching. Similarly, CD spectroscopy of the binding region of α‐agglutinin showed reversible conversion from β‐rich to mixed α/β structure at elevated temperatures or when the pH was changed. The reversibility of these changes implied that there is a small energy difference between the all‐β and the α/β states. Similar changes followed cleavage of peptide or disulfide bonds. Together, these observations imply that short sequences of high helical propensity are constrained to a β‐rich state by covalent and local charge interactions under native conditions, but form helices under non‐native conditions.