Hemoglobin subunit beta (HBB) (HBB)

Hemoglobin subunit beta (HBB) is a protein subunit that, along with alpha subunits, forms the heterotetrameric hemoglobin molecule essential for oxygen transport from the lungs to peripheral tissues (UniProt P68871). The Cysteine 93 residue of the beta chain (Cysβ93) is a highly conserved site that plays a pivotal role in the "third gas" function of hemoglobin: the transport and delivery of nitric oxide (NO) (Jia et al., Nature 1996). Through S-nitrosylation at Cysβ93, hemoglobin can sense oxygen gradients and release NO to induce vasodilation in hypoxic tissues, thereby regulating systemic blood pressure and regional blood flow (Gladwin et al., Free Radic Biol Med 2000). In diseases such as sickle cell anemia and beta-thalassemia, mutations or oxidative stress affecting HBB and the Cysβ93 residue lead to impaired gas exchange and vascular complications (PubMed 11090345). Pharmacological targeting of this site or the HBB subunit involves modulating oxygen affinity or restoring NO bioavailability to treat cardiovascular and hematologic disorders (PubChem CID 7067855). This residue is particularly significant as its modification can allosterically influence the transition between the oxygenated R-state and deoxygenated T-state of the hemoglobin tetramer.

Other names

Beta-globinHemoglobin beta chainHemoglobin Cysβ93HBB

S-nitrosylation of Cysβ93 and allosteric modulation of oxygen affinity