Hemoglobin

HBQ1 is a member of the Hemoglobin family. Hemoglobin is a 66.7 kDa protein attached to four iron-binding, methenelinked tetrapyrrole rings (heme). The globin part of Hemoglobin contains 2 alpha chains and 2 beta chains organized as couples creating a tetramer. Every one of the 4 globin chains covalently connects with a heme group. The bonds between alpha and beta chains are frailer than between parallel globin chains, thus creating a cleavage plane which is vital for oxygen binding and release. Relaxation of the alpha1-beta2 cleavage plane results in high affinity for oxygen.

Hemoglobin subunit gamma-2 (HBG2), is a member of the globin family. HBG2 belongs to the fetal hemoglobin subunit, which comprised of two alpha chains organized with 2 gamma chains. HBG2 Amplified fetal hemoglobin production in adults and improve the clinical severity of sickle cell disease and beta-thalassemia major.

The gamma globin genes which are HBG1 and HBG2, usually expressed in the fetal liver, spleen and bone marrow. 2 gamma chains together along with 2 alpha chains comprise fetal hemoglobin (HbF) which is normally replaced by mature hemoglobin (HbA) at birth. Gamma chain production continues into adulthood in several beta-thalassemias and linked situations. The two types of gamma chains differ at residue 136 where glycine is found in the G-gamma product (HBG2) and alanine is found in the A-gamma product (HBG1). The former is predominant at birth.

HBA2 is a member of the globin family. HBA2 takes part in oxygen transport from the lung to the different peripheral tissues. The coding sequences of HBA2 and HBA1 are equal but have a small difference over the 5' untranslated regions and the introns, and a large difference over the 3' untranslated regions. HbA is constituted from two alpha chains and two beta chains which in standard adult life hold about 97% of the total hemoglobin; alpha chains associate with delta chains to create HbA-2 that with HbF (fetal hemoglobin) form the remaining 3% of adult hemoglobin. Alpha thalassemia is caused by removal of each of the alpha genes or removal of both HBA2 and HBA1; nondeletion alpha thalassemias has also been reported.

The HbA1c shows the average amount of glucose in the blood over a period of 3 months. Sugar in the bloodstream can become attached to the hemoglobin in red blood cells (glycosylation). Once the sugar is attached, it stays there for the life of the red blood cell, which is about 120 days. The higher the level of blood sugar, the more sugar attaches to red blood cells. The HbA1c is formed in a non-enzymatic pathway by hemoglobin's standard exposure to elevated plasma levels of glucose. HbA1c is tested to monitor nephropathy and retinopathy in diabetes mellitus.

Alpha-hemoglobin stabilizing protein (AHSP) is an erythroid-specific protein that acts as a chaperone to prevent the aggregation of A-hemoglobin during normal erythroid cell development. AHSP specifically protects free A-hemoglobin from precipitation in live cells and in solution. AHSP is expected to modulate pathological states of alpha-hemoglobin excess such as beta-thalassemia. Furthermore, AHSP promotes alpha globin chain stability in human erythropoiesis. In addition, the AHSP stabilizes the alpha-Hb chain, thus avoiding its precipitation and its ability to generate ROS, which is implicated in cell death. AHSP is expressed in blood and bone marrow. AHSP subunit is a monomer, it forms a heterodimer with free alpha-hemoglobin. On the other hand, AHSP does not bind beta-hemoglobin nor alpha2beta2 hemoglobin A. AHSP is downregulated in TSEs (transmissible spongiform encephalopathies).

Hemoglobin Subunit Zeta (Hbz) or Hba-x is a alpha-like hemoglobin and part of the globin family. The protein is expressed and produced in the the yolk sac in early stages of embryonic development. Hemoglobin subunit zeta has 2 pseudogenes and 5 functional genes.

Hemoglobin subunit zeta (HBZ) is part of the globin family. Hemoglobin Zeta is alpha-like hemoglobin. The HBZ polypeptide is synthesized in the yolk sac of the early embryo, while alpha-globin is produced throughout fetal and adult life.