Chemistry Department and Industrial Biotechnology Program, University of Puerto Rico, Mayagüez, Puerto Rico.
Natural Sciences Department, University of Puerto Rico, Aguadilla, Puerto Rico.
Biopolymers. 2021 Jun;112(6):e23427. doi: 10.1002/bip.23427. Epub 2021 Apr 1.
Hemoglobin III (HbIII) is one of the two oxygen reactive hemoproteins present in the bivalve, Lucina pectinata. The clam inhabits a sulfur-rich environment and HbIII is the only hemoprotein present in the system which does not yet have a structure described elsewhere. It is known that HbIII exists as a heterodimer with hemoglobin II (HbII) to generate the stable Oxy(HbII-HbIII) complex but it remains unknown if HbIII can form a homodimeric species. Here, a new chromatographic methodology to separate OxyHbIII from the HbII-HbIII dimer has been developed, employing a fast performance liquid chromatography and ionic exchange chromatography column. The nature of OxyHbIII in solution at concentrations from 1.6 mg/mL to 20.4 mg/mL was studied using small angle X-ray scattering (SAXS). The results show that at all concentrations, the Oxy(HbIII-HbIII) dimer dominates in solution. However, as the concentration increases to nonphysiological values, 20.4 mg/mL, HbIII forms a 30% tetrameric fraction. Thus, there is a direct relationship between the Oxy(HbIII-HbIII) oligomeric form and hemoglobin concentration. We suggest it is likely that the OxyHbIII dimer contributes to active oxygen transport in tissues of L pectinata, where the Oxy(HbII-HbIII) complex is not present.
血红蛋白 III（HbIII）是双壳类软体动物，珠蚌中存在的两种氧反应性血红素蛋白之一。该蚌栖息在富含硫的环境中，HbIII 是该系统中唯一尚未在其他地方描述过结构的血红素蛋白。已知 HbIII 与血红蛋白 II（HbII）形成异二聚体以生成稳定的 Oxy（HbII-HbIII）复合物，但尚不清楚 HbIII 是否可以形成同二聚体。在这里，开发了一种新的色谱方法来分离 OxyHbIII 与 HbII-HbIII 二聚体，采用快速高效液相色谱和离子交换色谱柱。使用小角度 X 射线散射（SAXS）研究了浓度为 1.6mg/mL 至 20.4mg/mL 的 OxyHbIII 在溶液中的性质。结果表明，在所有浓度下，Oxy（HbIII-HbIII）二聚体在溶液中占主导地位。然而，随着浓度增加到非生理值 20.4mg/mL，HbIII 形成 30%的四聚体部分。因此，Oxy（HbIII-HbIII）寡聚形式与血红蛋白浓度之间存在直接关系。我们认为，OxyHbIII 二聚体可能有助于 L pectinata 组织中的活性氧运输，其中不存在 Oxy（HbII-HbIII）复合物。
