Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Chembiochem. 2012 Apr 16;13(6):879-87. doi: 10.1002/cbic.201100808.
α(1)-Microglobulin (α(1)m) is a 26 kDa plasma and tissue protein belonging to the lipocalin protein family. Previous investigations indicate that the protein interacts with heme and suggest that it has a function in heme metabolism. However, detailed characterizations of the α(1)m-heme interactions are lacking. Here, we report for the first time the preparation and analysis of a stable α(1)m-heme complex upon carbamidomethylation of the reactive Cys34 by using recombinantly expressed human α(1)m. Analytical size-exclusion chromatography coupled with a diode-array absorbance spectrophotometry demonstrates that at first an α(1)m-heme monomer is formed. Subsequently, a second heme triggers oligomerization that leads to trimerization. The resulting (α(1)mheme)(3) complex was characterized by resonance Raman and EPR spectroscopy, which support the presence of two ferrihemes, thus indicating an unusual spin-state admixed ground state with S=(3)/(2), (5)/(2).
α(1)-微球蛋白 (α(1)m) 是一种 26kDa 的血浆和组织蛋白，属于脂质运载蛋白家族。先前的研究表明，该蛋白与血红素相互作用，并表明其在血红素代谢中具有功能。然而，α(1)m-血红素相互作用的详细特征尚不清楚。在这里，我们首次报道了通过重组表达的人α(1)m 对反应性半胱氨酸 34 的氨基甲酰化，制备和分析稳定的α(1)m-血红素复合物。分析性大小排阻色谱法与二极管阵列吸收分光光度法联用表明，首先形成α(1)m-血红素单体。随后，第二个血红素触发寡聚化，导致三聚体化。所得的(α(1)mheme)(3)复合物通过共振拉曼和 EPR 光谱进行了表征，这支持存在两个亚铁血红素，从而表明存在一种异常的混合自旋态基态，S=(3)/(2)、(5)/(2)。
