The circularly permuted globin domain of Androglobin

Androglobin, is a recently discovered circularly permuted, multi-domain is hemoglobin. Using a remote homologue alignment method, coupled with molecular modelling and molecular dynamics, we identified the alignment to other hemoglobins. This guided the first stable recombinant expression of an androglobin domain and the first structural and biochemical characterization of the globin domain of androglobin, which is split by an IQ domain. Tyrosine is found in place of the highly conserved phenylalanine that resides in the highly conserved CD1 position, a structural feature unknown in eukaryotes but common in prokaryotic globins. As expressed, the heme iron is hexacoordinate in the ferrous form but partially pentacoordinate in the ferric form. Exceptional in the globin superfamily, but similar to other hemoproteins such as cytochrome c’, the heme iron binds nitric oxide as a five coordinate complex. This work expands our knowledge of the fundamental chemistry of this hitherto elusive medically important protein.