Cyclostome Hemoglobins Are Possibly Paralogous to Gnathostome Hemoglobins

Dimeric hemoglobins in lampreys are thought to be orthologous to gnathostome hemoglobins, comprising a familiar tetrameric assembly, despite their different subunit interface. To elucidate this contradictory problem, a phylogenetic analysis of vertebrate globins was conducted. The inferred maximum-likelihood trees revealed that the cyclostome hemoglobins are closely related to STAPs, recently identified stellate cell activation-associated proteins, and are paralogous to gnathostome hemoglobins. The quaternary structural difference between cyclostome and gnathostome hemoglobins is well understandable in light of their paralogous relationship.