Mole rat hemoglobin: primary structure and evolutionary aspects in a second karyotype of Spalax ehrenbergi, Rodentia, (2n = 52)

Abstract

The hemoglobins of the four karyotypes of Spalax ehrenbergi (2n = 52, 54, 58, 60) did not show any differences in their electrophoretic pattern and in high performance liquid chromatography. The complete amino-acid sequence of mole rat hemoglobin (Spalax ehrenbergi), chromosome species 2n = 52, is presented. It was elucidated by automatic Edman degradation of the chains, the tryptic peptides, and the C-terminal peptide obtained by acid hydrolysis of the Asp-Pro bond in beta-chains. The alpha- and beta-chains are identical with those of the chromosome species 2n = 60. A comparison of the hemoglobins of mole rat, mouse, and other rodents shows homology but no indication of adaptation to subterranean life. In all probability alpha 11(A9)Arg and alpha 120(H3)Gly, unique in mole rat among all mammalian hemoglobins, are not involved in high oxygen affinity. The construction of a phylogenetic tree by the maximum parsimony method, based on hemoglobin sequences, made it possible to show that Rodentia originated as a monophyletic clade, and to find the phylogenetic relationship of Spalacidae to other Rodentia (Mus, Rattus, Ondatra, Mesocricetus, Citellus, and Cavia). Among all rodents the slowest rate of nucleotide replacements occurred in the lineage to Spalax (20%) and the fastest in the lineage to Cavia (59%).