Institute of Zoology, Johannes Gutenberg University, Mainz, Germany.
IUBMB Life. 2011 May;63(5):323-8. doi: 10.1002/iub.453. Epub 2011 Apr 13.
The extracellular hemoglobin multimer of the planorbid snail Biomphalaria glabrata, intermediate host of the human parasite Schistosoma mansoni, is presumed to be a 1.44 MDa complex of six 240 kDa polypeptide subunits, arranged as three disulfide-bridged dimers. The complete amino acid sequence of two subunit types (BgHb1 and BgHb2), and the partial sequence of a third type (BgHb3) are known. Each subunit encompasses 13 paralogus heme domains, and N-terminally a smaller plug domain responsible for subunit dimerization. We report here the recombinant expression of different functional fragments of BgHb2 in Escherichia coli, and of the complete functional subunits BgHb1 and BgHb2 in insect cells; BgHb1 was also expressed as disulfide-bridged dimer (480 kDa). Oxygen-binding measurements of the recombinant products show a P(50) of about 7 mmHg and the absence of a significant cooperativity or Bohr effect. The covalently linked dimer of BgHb1, but not the monomer, is capable to form aggregates closely resembling native BgHb molecules in the electron microscope.
布氏嗜碘吸虫的中间宿主光滑河滨螺的细胞外血红蛋白多聚体被认为是一个由六个 240 kDa 多肽亚基组成的 1.44 MDa 复合物，排列为三个二硫键桥接的二聚体。两种亚基类型（BgHb1 和 BgHb2）的完整氨基酸序列以及第三种亚基类型（BgHb3）的部分序列已知。每个亚基包含 13 个同源血红素结构域，以及负责亚基二聚化的较小的插头结构域。我们在此报告了 BgHb2 的不同功能片段在大肠杆菌中的重组表达，以及完整功能亚基 BgHb1 和 BgHb2 在昆虫细胞中的表达；BgHb1 也被表达为二硫键桥接的二聚体（480 kDa）。重组产物的氧结合测量显示 P(50)约为 7 mmHg，并且没有明显的协同作用或波尔效应。BgHb1 的共价连接二聚体（而不是单体）能够形成类似于电子显微镜中天然 BgHb 分子的聚集物。
