Hb Marseille [alpha 2 beta 2 N methionyl-2 (NA2) His----Pro]: a new beta chain variant having an extended N-terminus.

A new abnormal hemoglobin was found in a diabetic Maltese woman by citrate agar electrophoresis. This variant was undetectable by isoelectric focusing. No hematological abnormalities were observed. The structural analysis included isolation of the abnormal beta chain, high pressure liquid chromatography of the corresponding tryptic peptides and then microsequencing of the abnormal T1. These procedures revealed a double abnormality: the presence of a methionyl residue extending the NH2 terminus and a histidine to proline substitution in position NA2.