His87

His87 is a specific position within the human hemoglobin protein. Hemoglobin is a complex protein responsible for transporting oxygen from the lungs to the rest of the body and carbon dioxide back to the lungs. It is composed of four subunits, typically two alpha-globin chains and two beta-globin chains. Each subunit contains a heme group, which is an iron-containing molecule that binds to oxygen.

The notation "His87" refers to the 87th amino acid residue, which is histidine, in the beta-globin chain of hemoglobin. Histidine is an amino acid with a unique imidazole side chain that can act as both an acid and a base. In hemoglobin, histidine residues play crucial roles in maintaining the protein's structure and function, particularly in the binding and release of oxygen.

Specifically, His87 in the beta-globin chain is known as the "proximal histidine." This residue is directly coordinated to the iron atom within the heme group. This close interaction is essential for stabilizing the heme and facilitating the reversible binding of oxygen to the iron. Without the proper positioning and chemical properties of His87, hemoglobin's ability to effectively carry oxygen would be severely compromised. Mutations or alterations at this position can lead to significant hemoglobinopathies, conditions characterized by abnormal hemoglobin function, which can have serious health implications.