Gisela Liljeqvist

Hemoglobins, XLVIIII: The Primary Structure of a Monomeric Hemoglobin from the Hagfish,Myxine glutinosa L.: Evolutionary Aspects and Comparative Studies of the Function with Special Reference to the Heme Linkage

SummaryHagfish hemoglobin has three main components, one of which is Hb III. It is monomeric and consists of 148 amino acid residues (M = 17 350). Its complete primary structure, previously published, is discussed here. The proximal amino acid (F8) of the heme linkage is histidine as always in the hemoglobins, but the regularly expected distal histidine E7 is substituted by glutamine. This substitution, leading to a new kind of heme linkage, has hitherto only been demonstrated in opossum hemoglobin. It is suggested that E7, Gln, is directed out of the heme pocket, and that the adjacent Ell, Ile, is directed toward the inside of the pocket, giving the distal heme contact instead of histidine.Myxine Hb III has an additional tail of 9 amino acid residues at its N-terminal end, as has the hemoglobin ofLampetra fluviatilis. The genetic codes ofMyxine andLampetra hemoglobins show 117 differences, in spite of many morphological resemblances between hagfish and lamprey. Their primary hemoglobin structures show differences substantial enough to bo compatible with the divergence of the two families some 400–500 million years ago.

The hemoglobins of Myxine glutinosa L.—II. amino acid analyses, end group determinations and further investigations

Abstract 1. 1. The amino acid composition of the three main hemoglobins, Hb I, Hb II and Hb III, of the hagfish (Myxine glutinosa L.) has been determined. The composition differs so much from that of the lamprey (Lampertra fluviatilis) hemoglobin that a diphyletic origin of the two species seems likely. 2. 2. The N-terminal residue of Hb III (hagfish) is proline as in also that of lamprey hemoglobin. The N-terminal group of Hb I and II seems to be blocked. 3. 3. Because the three main hagfish hemoglobins have different molecular weights the amino acid composition is not sufficient for a discussion of their phylogenetic interrelationship but consideration of the amino acid sequences would be necessary.

The hemoglobins of myxine glutinosa L.—I. P+reparation and crystallization

Abstract 1. 1. Methods have been developed for the isolation of hagfish hemoglobin. 2. 2. Three main hemoglobin fractions have been separated by isoelectric focusing and two of these, named Hb I and Hb III, have been crystallized. 3. 3. The polymorphism of the hagfish hemoglobin is discussed.

Crystalline hagfish cytochrome-c

Abstract 1. 1. Cytochrome- c was crystallized from skeletal hagfish ( Myxine glutinosa ) muscles. 2. 2. The position of the absorption maxima of its reduced spectrum coincides in the visible range with those of cytochromes from other vertebrate species, except for the Soret band at 414 nm. 3. 3. Some interesting features of its amino acid composition are described. 4. 4. The N -terminal group is blocked and the C -terminal one is supposed to be lysine.

ESR Studies on the Nitrosyl Complex of Hagfish (Myxine glutinosa L.) Hemoglobin

Abstract The nitric oxide complex of hagfish hemoglobin exhibits electron spin resonance spectra centered around g = 2 with rhombic symmetry. The six coordinated spectrum is not influenced by protonation or presence of inositol hexaphosphate. Thus, the critical substitutions at E 7 (His → Gln) and E 11 (Yal → Ile) do not disrupt the proximal histidineiron bonds in the nitrosyl complex of this primitive hemoglobin, though the same type of substitution are known to cause destabilization of R quaternary structure in tetrameric mammalian nitrosylhemoglobins. This difference could be related to the difference in tension existing in the respective hemes of tetrameric and monomeric hemoglobins.