Pervanova K, Idakieva K, Stoeva S, Genov N, Voelter W
Institute of Organic Chemistry, Bulgarian Academy of Sciences, Sofia.
Spectrochim Acta A Mol Biomol Spectrosc. 2000 Feb 15;56(3):615-22. doi: 10.1016/s1386-1425(99)00261-9.
Molecular aggregates of the Rapana thomasiana hemocyanin are composed of two structural subunits, RHSS1 and RHSS2, each of which contains eight functional units (FUs) reversibly binding dioxygen. Multiunit fragments and individual 50-60 kDa FUs from RHSS2 were isolated and characterized by electron and fluorescence spectroscopy. The units have similar fluorescence parameters demonstrating that the tryptophyl side chains are located in the hydrophobic core of the globular folded regions. The copper-dioxygen system at the binuclear active site stabilizes considerably the native protein structure and quenches the indole emission. The removal of this system decreased the 'melting points' drastically Tm by 13-20 degrees C and increased 2-4 times the fluorescence quantum yields. The individual FUs differ considerably in their thermostability. The activation energy for the thermal deactivation of the excited tryptophyl residues of the apo-FUs is lower compared to that of the whole molluscan apo-Hcs.
唐冠螺血蓝蛋白的分子聚集体由两个结构亚基RHSS1和RHSS2组成，每个亚基包含八个可逆结合双原子氧的功能单元（FU）。从RHSS2中分离出多单元片段和单个50 - 60 kDa的FU，并通过电子和荧光光谱对其进行表征。这些单元具有相似的荧光参数，表明色氨酸侧链位于球状折叠区域的疏水核心中。双核活性位点处的铜 - 双原子氧体系相当大地稳定了天然蛋白质结构并猝灭了吲哚发射。去除该体系会使“熔点”大幅降低，Tm降低13 - 20摄氏度，并使荧光量子产率提高2 - 4倍。单个FU的热稳定性差异很大。与整个软体动物脱辅基血蓝蛋白相比，脱辅基FU中激发态色氨酸残基热失活的活化能更低。
