The polymeric hemoglobin molecule of Artemia. Interpretation of translated cDNA sequence of nine domains

Translated cDNA for Artemia hemoglobin provided sequence data for almost nine domains, from the fourth residue of the A helix of one domain through 1405 residues to a stop codon after the ninth domain. The domain sequences were all different (homology between pairs 17-38%) but aligned well with each other and with conventional globins, satisfying the requirements for Phe at CD1, His at F8 and most other highly conserved features of globins including His at E7. Features found to be characteristic of Artemia globin and present in all nine domains were Phe at B10, Tyr at C4, Gly at F5, Phe at G5 and Gly at H22. Approximately 14 residues including a consensus -Val-Asp-Pro-Val-Thr-Gly-Leu- were available to form the linker between each pair of domains. The Artemia sequence data were compared with the crystal structures of Chironomus thummi thummi erythrocruorin III and sperm whale myoglobin in order to identify features of structural similarity and to examine the consequences of the differences. The Artemia sequences were compatible with the main helices and critical features of the globin fold. Possible modifications to the C helix, FG turn, and GH turn were studied in terms of molecular coordinates.