Hemoglobin Providence. A human hemoglobin variant occurring in two forms in vivo

Area of Science:

• Biochemistry
• Genetics
• Molecular Biology

Background:

• Human hemoglobin structure and function are critical for oxygen transport.
• Genetic mutations can lead to abnormal hemoglobin variants with altered properties.
• The beta 82 lysine residue is crucial for 2,3-diphosphoglycerate binding.

Purpose of the Study:

• To characterize two novel abnormal hemoglobins, Hemoglobin Providence Asn and Hemoglobin Providence Asp.
• To elucidate the genetic basis and molecular alterations of these hemoglobin variants.
• To investigate the significance of substitutions at the invariant beta 82 position.

Main Methods:

• Electrophoresis (cellulose acetate, citrate agar, globin chain) was used to separate and identify hemoglobin variants.
• Amino acid sequence analysis was performed to determine the specific substitutions in the beta chains.
• Hemolysate analysis from affected patients was conducted.

Main Results:

• Two abnormal hemoglobins, Hemoglobin Providence Asn and Asp, were identified, arising from a single genetic change.
• The mutation substitutes lysine with asparagine at position beta 82.
• Hemoglobin Providence Asp results from in vivo deamidation of asparagine to aspartic acid at beta 82.
• Electrophoretic and sequence analyses confirmed the presence of three beta chains, including normal beta A and two abnormal variants.

Conclusions:

• The study identified and characterized two new abnormal human hemoglobins, Hemoglobin Providence Asn and Asp.
• These variants result from a rare substitution at the invariant beta 82 position, affecting a key site for 2,3-diphosphoglycerate binding.
• The findings highlight the structural and potential functional implications of mutations at this critical hemoglobin residue.