cd08925: Hb-beta_like (this model, PSSM-Id:271276 is obsolete and has been replaced by 381262)
Hemoglobin beta, gamma, delta, epsilon, and related Hb subunits
Hb is the oxygen transport protein of erythrocytes. It is an allosterically modulated heterotetramer. Hemoglobin A (HbA) is the most common Hb in adult humans, and is formed from two alpha-chains and two beta-chains (alpha2beta2). An equilibrium exists between deoxygenated/unliganded/T(tense state) Hb having low oxygen affinity, and oxygenated /liganded/R(relaxed state) Hb having a high oxygen affinity. Various endogenous heterotropic effectors bind Hb to modulate its oxygen affinity and cooperative behavior, e.g. hydrogen ions, chloride ions, carbon dioxide and 2,3-bisphosphoglycerate. Hb is also an allosterically regulated nitrite reductase; the plasma nitrite anion may be activated by hemoglobin in areas of hypoxia to bring about vasodilation. Other Hb types are: HbA2 (alpha2delta2) which in normal individuals, is naturally expressed at a low level; Hb Portland-1 (zeta2gamma2), Hb Gower-1 (zeta2epsilon2), and Hb Gower-2 (alpha2epsilon2), which are Hbs present during the embryonic period; and fetal hemoglobin (HbF, alpha2gamma2), the primary hemoglobin throughout most of gestation. These Hbs types have differences in O2 affinity and in their interactions with allosteric effectors.
Jiyao W et al.(2023). "The conserved domain database in 2023.",