α78(EF7)Asn→Asp is a Posttranslational Modification in Hb J-Singapore [α78(EF7)Asn→Asp;α79(EF8)Ala→Gly]

Abstract

In Hb J-Singapore, the α78(EF7)Asn→Asp and α79(EF8)Ala→Gly substitutions were initially thought to be genetic mutations. Subsequent studies on other similar hemoglobin variants suggested that the Asn→Asp change was a posttranslational modification. Nevertheless, lack of DNA evidence made it difficult to confirm the deamidation in Hb J-Singapore. We recently encountered a female patient with Hb J-Singapore trait. In this report, we present electrospray mass spectrometry and DNA data to confirm the α78(EF7)Asn→Asp is indeed a posttranslational modification.

Keywords:

• Hemoglobin (Hb) variant
• Electrospray ionization mass spectrometry (ESI/MS)
• DNA sequencing
• Hb J-Singapore
• Deamidation
• Posttranslational modification