Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, Australia.
Centre for Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Parkville, Australia.
FEBS Lett. 2024 Sep;598(18):2240-2248. doi: 10.1002/1873-3468.14958. Epub 2024 Jun 16.
Haemoglobin (Hb) is a vital oxygen carrier in vertebrates. Low blood Hb levels may indicate anaemia or genetic disorders, while its presence in the lower digestive system suggests colon cancer. Detecting and quantifying human Hb is essential for medical diagnostics. A nanobody-based sandwich-ELISA test was recently developed utilising llama-derived nanobodies NbE11 and NbB9. These nanobodies specifically bind to human Hb without cross-reacting with Hb from other vertebrates. Here, we determine the crystal structure of NbE11 in complex with human Hb. NbE11 binds Hb with high affinity, predominantly binding the β-Hb subunit. Structural differences between human Hb and other vertebrates at the NbE11 binding interface likely explain the assay's lack of cross-reactivity, providing insights for developing Hb binding diagnostics.
血红蛋白（Hb）是脊椎动物中至关重要的氧气载体。血液中 Hb 水平低可能表明贫血或遗传疾病，而在下消化道中存在 Hb 则提示结肠癌。检测和定量人体 Hb 对于医学诊断至关重要。最近开发了一种基于纳米抗体的夹心 ELISA 测试，该测试利用了来源于骆驼的纳米抗体 NbE11 和 NbB9。这些纳米抗体特异性地与人 Hb 结合，而不会与其他脊椎动物的 Hb 发生交叉反应。在这里，我们确定了 NbE11 与人 Hb 复合物的晶体结构。NbE11 与人 Hb 具有高亲和力结合，主要结合β-Hb 亚基。在 NbE11 结合界面处，人 Hb 与其他脊椎动物之间的结构差异可能解释了该测定缺乏交叉反应性，为开发 Hb 结合诊断方法提供了见解。
