Structure-function relationships in the low-affinity mutant haemoglobin Aalborg (Gly74 (E18)beta----Arg)

Biophysical chemistry behind sickle cell anemia and the mechanism of voxelotor action

Sickle cell anemia disease has been a great challenge to the world in the present situation. It occurs only due to the polymerization of sickle hemoglobin (HbS) having Pro-Val-Glu typed mutation, while the polymerization does not occur in normal hemoglobin (HbA) having Pro-Glu-Glu peptides. It is also well confirmed that the oxygenated HbS (OHbS) does not participate in the polymerization, while the deoxygenated HbS (dHbS) does, which causes the shape of red blood cells sickled. After polymerization, the blood has a low oxygen affinity. Keeping this fact into consideration, only those drugs are being synthesized that stabilize the OHbS structure so that the polymerization of HbS can be stopped. The literature data showed no systematic description of the changes occurring during the OHbS conversion to dHbS before polymerization. Hence, an innovative reasonable study between HbA and HbS, when they convert into their deoxygenated forms, was done computationally. In this evaluation, physiochemical parameters in HbA/HbS before and after deoxygenation were studied and compared deeply. The computationally collected data was used to understand the abnormal behaviour of dHbS arising due to the replacement of Glu6 with Val6. Consequently, during the presented computational study, the changes occurring in HbS were found opposite/abnormal as compared to HbA after the deoxygenation of both. The mechanism of Voxelotor (GBT-440) action to stop the HbS polymerization was also explained with the help of computationally collected data. Besides, a comparative study between GBT-440 and another suggested drug was also done to know their antisickling strength. Additionally, the effect of pH, CO, CO2, and 2,3-diphosphoglycerate (2,3-DPG) on HbS structure was also studied computationally.

Hemoglobin variant (hemoglobin Aalborg) mimicking interstitial pulmonary disease

Hemoglobin Aalborg is a moderately unstable hemoglobin variant with no affiliation to serious hematological abnormality or major clinical symptoms under normal circumstances. Our index person was a healthy woman of 58, not previously diagnosed with hemoglobinopathy Aalborg, who developed acute respiratory failure after a routine cholecystectomy. Initially she was suspected of idiopathic interstitial lung disease, yet a series of tests uncovered various abnormal physiological parameters and set the diagnosis of hemoglobinopathy Aalborg. This led us to examine a group of the index person's relatives known with hemoglobinopathy Aalborg in order to study whether the same physiological abnormalities would be reencountered. They were all subjected to spirometry and body plethysmography, six-minute walking test, pulse oximetry, and arterial blood gas samples before and after the walking test. The entire study population presented the same physiological anomalies: reduction in diffusion capacity, and abnormalities in P(a)O2 and p50 values; the latter could not be presented by the arterial blood gas analyzer; furthermore there was concordance between pulse oximetry and arterial blood gas samples regarding saturation. These data suggest that, based upon the above mentioned anomalies in physiological parameters, the diagnosis of hemoglobinopathy Aalborg should be considered.

Crystal structure of haemoglobin from donkey (Equus asinus) at 3Å resolution

Haemoglobin from donkey was purified and crystallized in space group C2. The present donkey haemoglobin model comprises of two subunits alpha and beta. These alpha and beta subunits comprise of 141 and 146 amino acid residues, respectively, and the haem groups. The donkey haemoglobin differs from horse only in two amino acids of alpha-chain (His20 to Asn and Tyr24 to Phe) and these substitutions do not significantly change the secondary structural features of donkey haemoglobin. The haem group region and subunit contacts are closely resemble with that of horse methaemoglobin.