Members of the hemoglobin (Hb) superfamily are present in nerve tissue of several vertebrate and invertebrate species. In vertebrates they display hexacoordinate heme iron atoms and are typically expressed at low levels (μm). Their function is still a matter of debate. In invertebrates they have a hexa- or pentacoordinate heme iron, are mostly expressed at high levels (mm), and have been suggested to have a myoglobin-like function. The native Hb of the surf clam, Spisula solidissima, composed of 162 amino acids, does not show specific deviations from the globin templates. UV-visible and resonance Raman spectroscopy demonstrate a hexacoordinate heme iron. Based on the sequence analogy, the histidine E7 is proposed as a sixth ligand. Kinetic and equilibrium measurements show a moderate oxygen affinity (P50 ∼0.6 torr) and no cooperativity. The histidine binding affinity is 100-fold lower than in neuroglobin. Phylogenetic analysis demonstrates a clustering of the S. solidissima nerve Hb with mollusc Hbs and myoglobins, but not with the vertebrate neuroglobins. We conclude that invertebrate nerve Hbs expressed at high levels are, despite the hexacoordinate nature of their heme iron, not essentially different from other intracellular Hbs. They most likely fulfill a myoglobin-like function and enhance oxygen supply to the neurons. Members of the hemoglobin (Hb) superfamily are present in nerve tissue of several vertebrate and invertebrate species. In vertebrates they display hexacoordinate heme iron atoms and are typically expressed at low levels (μm). Their function is still a matter of debate. In invertebrates they have a hexa- or pentacoordinate heme iron, are mostly expressed at high levels (mm), and have been suggested to have a myoglobin-like function. The native Hb of the surf clam, Spisula solidissima, composed of 162 amino acids, does not show specific deviations from the globin templates. UV-visible and resonance Raman spectroscopy demonstrate a hexacoordinate heme iron. Based on the sequence analogy, the histidine E7 is proposed as a sixth ligand. Kinetic and equilibrium measurements show a moderate oxygen affinity (P50 ∼0.6 torr) and no cooperativity. The histidine binding affinity is 100-fold lower than in neuroglobin. Phylogenetic analysis demonstrates a clustering of the S. solidissima nerve Hb with mollusc Hbs and myoglobins, but not with the vertebrate neuroglobins. We conclude that invertebrate nerve Hbs expressed at high levels are, despite the hexacoordinate nature of their heme iron, not essentially different from other intracellular Hbs. They most likely fulfill a myoglobin-like function and enhance oxygen supply to the neurons. The recent discovery of globin proteins in the nerve cells of mammals and other vertebrates (1Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar) has created much interest in unraveling the cellular functions and potential biomedical implications of these oxygen binding molecules in the metabolism of the vertebrate nervous system (2Hankeln T. Ebner B. Fuchs C. Gerlach F. Haberkamp M. Laufs T.L. Roesner A. Schmidt M. Weich B. Wystub S. Saaler-Reinhardt S. Reuss S. Bolognesi M. de Sanctis D. Marden M.C. Kiger L. Moens L. Dewilde S. Nevo E. Avivi A. Weber R.E. Fago A. Burmester T. J. Inorg. Biochem. 2005; 99: 110-119Crossref PubMed Scopus (258) Google Scholar). Historically, however, “nerve hemoglobins” (nHbs) 4The abbreviations used are: nHb, invertebrate nerve hemoglobin; Mb, myoglobin; Ngb, neuroglobin; Cygb, cytoglobin; HS, high spin; RR, resonance raman; RT, reverse transcription; P50, oxygen pressure at which half saturation of the hemoglobin is obtained. were first observed in invertebrate taxa. In 1872, Lankester had already recorded the brilliant red color of the ganglia of the polychaete annelid Aphrodite aculeata (3Lankester E.R. Proc. R. Soc. Lond. B Biol. Sci. 1872; 21: 70-81Google Scholar). Since then, nHbs have also been found in, or associated with, nerve tissues of several other invertebrate taxa, such as molluscs, arthropods, nemerteans, and nematode species (4Wittenberg J.B. Advances in Comparative and Environmental Physiology.in: Mangum C.P. Springer-Verlag Berlin, Heidelberg1992: 59-85Google Scholar, 5Weber R.E. Vinogradov S.N. Physiol. Rev. 2001; 81: 569-628Crossref PubMed Scopus (414) Google Scholar). Of these, only the nHbs of A. aculeata (6Dewilde S. Blaxter M. Van Hauwaert M.L. Vanfleteren J. Esmans E.L. Marden M. Griffon N. Moens L. J. Biol. Chem. 1996; 271: 19865-19870Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar) and the nemertean worm Cerebratulus lacteus (7Vandergon T.L. Riggs C.K. Gorr T.A. Colacino J.M. Riggs A.F. J. Biol. Chem. 1998; : 16998-17011Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar) have been characterized at the molecular level. With few exceptions (e.g. in air-breathing gastropods), the invertebrate nHbs are expressed at high concentrations (in the mm range) and have therefore been suggested to support nerve function by mediating O2 storage and/or transport during temporary hypoxia (4Wittenberg J.B. Advances in Comparative and Environmental Physiology.in: Mangum C.P. Springer-Verlag Berlin, Heidelberg1992: 59-85Google Scholar). For example, in the gastropod mollusc Aplysia depilans, the oxygenation state of the nHb was correlated with the electrical activity of the neural ganglia, and firing was shown to be proportional to the degree of oxygenation of the globin (8Chalazonitis N. Gola M. Arvanitaki A. C. R. Seances Soc. Biol. Fil. 1966; 160: 1020-1023PubMed Google Scholar). The nHb in the nerve bundles of the bivalve mollusc Tellina alternata was reported to extend the time of O2 delivery to the nerves during anoxic periods by as much as 30 min, whereas this effect was not demonstrable in the nerves of a related clam species Tagelius plebeius, which lack the nHb (9Kraus D.W. Colacino J.M. Science. 1986; 232: 90-92Crossref PubMed Scopus (43) Google Scholar). In many cases, the nHbs appear to be specifically expressed in the glial cells surrounding neurons, as reported for the clams T. alternata and Spisula solidissima (10Kraus D.W. Doeller J.E. Smith P.R. Biol. Bull. 1988; 174: 54-66Crossref PubMed Google Scholar), the water-dwelling gastropods Lymnaea stagnalis and Planorbis corneus (11Schindelmeiser I. Kuhlmann D. Nolte A. Comp. Biochem. Physiol. B. 1979; 64B: 149-154Crossref Scopus (11) Google Scholar), the nemertean C. lacteus (7Vandergon T.L. Riggs C.K. Gorr T.A. Colacino J.M. Riggs A.F. J. Biol. Chem. 1998; : 16998-17011Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar), and the annelid A. aculeata (12Wittenberg B.A. Briehl R.W. Wittenberg J.B. Biochem. J. 1965; 96: 363-371Crossref PubMed Scopus (57) Google Scholar). In Aplysia and in the air-breathing gastropods Helix pomatia and Cepaea nemoralis, however, the nHbs have been detected within the neurons themselves (11Schindelmeiser I. Kuhlmann D. Nolte A. Comp. Biochem. Physiol. B. 1979; 64B: 149-154Crossref Scopus (11) Google Scholar, 13Arvanitaki A. Chalazonitis N. Bull. Inst. Oceanogr. Monaco. 1960; 1164: 1-83Google Scholar). The physiological implications of this cell type-specific expression are With and (12Wittenberg B.A. Briehl R.W. Wittenberg J.B. Biochem. J. 1965; 96: 363-371Crossref PubMed Scopus (57) Google Scholar), the oxygen of nHbs are moderate and to of vertebrate in with the proposed oxygen supply function. different of nHbs on the at the heme iron. The nHbs of Aplysia A. aculeata and C. lacteus are vertebrate and whereas of the T. alternata and S. solidissima are hexacoordinate and a (9Kraus D.W. Colacino J.M. Science. 1986; 232: 90-92Crossref PubMed Scopus (43) Google Scholar, PubMed Scopus Google Scholar). In the E7 histidine the sixth of the heme iron and has to be be in binding of which the implications still have to be S. Kiger L. Burmester T. Hankeln T. T. Marden M.C. R. Moens L. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, L. J. Dewilde S. Burmester T. Hankeln T. Moens L. D. Marden M. PubMed Scopus Google Scholar). of these (e.g. moderate oxygen of invertebrate nHbs are with the which have been in many vertebrate taxa, and T. Haberkamp M. S. Roesner A. Schmidt M. Ebner B. Gerlach F. Fuchs C. Hankeln T. PubMed Scopus Google Scholar). is expressed in the and nervous the and in but is specifically found in neurons and not in or other glial cells S. Saaler-Reinhardt S. Weich B. Wystub S. Reuss Burmester T. Hankeln T. PubMed Scopus Google Scholar, E. I. D. Dewilde S. Moens L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M. A. Laufs T. Hankeln T. Burmester T. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, S. Laufs T. Schmidt M. Burmester T. Saaler-Reinhardt S. Hankeln T. Reuss S. PubMed Scopus Google Scholar, T.L. Wystub S. Reuss S. Burmester T. Saaler-Reinhardt S. Hankeln T. PubMed Scopus Google Scholar). In to most is expressed at lower concentrations in the vertebrate whereas is expressed in the M. A. Laufs T. Hankeln T. Burmester T. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). also a hexacoordinate heme (1Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar, A. Bolognesi M. A. Dewilde S. Moens L. Hankeln T. Burmester T. PubMed Scopus Google Scholar, L. Dewilde S. Nature. 2000; 407: PubMed Scopus Google Scholar, A. C. Dewilde S. Moens L. Weber R.E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). is to neurons in and in Proc. Sci. S. A. 2001; PubMed Scopus Google Scholar, A. L. Proc. Sci. S. A. PubMed Scopus Google Scholar). function is and several physiological of are still (2Hankeln T. Ebner B. Fuchs C. Gerlach F. Haberkamp M. Laufs T.L. Roesner A. Schmidt M. Weich B. Wystub S. Saaler-Reinhardt S. Reuss S. Bolognesi M. de Sanctis D. Marden M.C. Kiger L. Moens L. Dewilde S. Nevo E. Avivi A. Weber R.E. Fago A. Burmester T. J. Inorg. Biochem. 2005; 99: 110-119Crossref PubMed Scopus (258) Google Scholar). For of vertebrate and invertebrate nHb have at the molecular of the nHb of the surf clam S. solidissima PubMed Scopus Google Scholar, D.W. Doeller J.E. Biol. Bull. 1988; 174: Google Scholar, J.E. D.W. Biol. Bull. 1988; 174: PubMed Google Scholar). is of a hexacoordinate nHb, which is expressed in glial cells and the nerves of this a red solidissima were from the and and were in and at of the of S. solidissima were and in mm the and at the red was The nHb was by at and were to mm and for at were with and by on a mm a to in at a of The were and with at of The were on a mm the as for globin were by to the were the of and A. aculeata nHb as templates. nerve of S. solidissima were and in at was on nerve the was from of to the of the of was for the and for The were to of of the was the The of was to the of globin by S. solidissima nHb were on the sequence at the level. S. solidissima was the was and from is a with to the by the is a with to the by the was for at at at at for and at The was and Based on this sequence a was the of system for of The of the S. solidissima globin was from the by a the and the were to the by and were or the on by were on were and of the S. solidissima nHb of S. solidissima and of several was by the of Schmidt E.R. Scopus Google Scholar) with of were to the nHb and were were as of the of the nHb of S. solidissima in S. solidissima nHb were expressed as S. Kiger L. Burmester T. Hankeln T. T. Marden M.C. R. Moens L. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). In the of the nHb was the expression expression in E. the S. solidissima nHb was to by for which the was and mm a in mm mm and a in mm The globin were and of and S. solidissima S. solidissima nHb in mm was by The native or at mm was in in and were on a the The were by to the molecular of the the was with and S. solidissima nHb were by and native was as by the for and the with the were were and and Raman measurements were with a were in a from to measurements were on Raman of a in and a The was a at The was at to were and the of by a of and were of the was by of and the a with The was by and by of The of the used for and measurements was typically in Kinetic and of to and S. solidissima affinity and of nHb were in mm at and a as A. C. Dewilde S. Moens L. Weber R.E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). were to with the at was a with was in a for O2 affinity O2 at and were from the and the of is the O2 were by as J. Dewilde S. Burmester T. Hankeln T. Moens L. D. Marden M.C. Kiger L. J. Full Text Full Text PDF PubMed Scopus Google Scholar). of the was with at The to the a binding of the and the sixth ligand. were used to the different species. the of the and the on and for the ligand. In a a of and oxygen was used to the oxygen binding Phylogenetic of mollusc and the S. solidissima nHb were to of globin (1Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar, T. Ebner B. Weich B. Hankeln T. Biol. PubMed Scopus Google Scholar, B. Burmester T. Hankeln T. Biol. PubMed Scopus Google Scholar). The of mollusc Hbs and and and The the and Hb Hb Hb Hb and A. aculeata nHb nHb, Hbs to C. lacteus nHb and For the of the A. Biol. 1996; Scopus Google Scholar), J. of of Scholar), S. M. 2001; PubMed Scopus Google Scholar), and F. 2001; PubMed Scopus Google Scholar) were were with the S. N. Biol. 2001; PubMed Scopus Google Scholar) of sequence with of was with and that were for were were and were The were on the For N. M. Biol. Google Scholar), were the of and D. Scholar). The from the and were for In the of the was used for of The of the was by J. PubMed Google Scholar) with and of the S. solidissima nHb was from the sequence of by of the The sequence was by the of the nHb also the of the S. solidissima nHb with related globin amino of the globin such as and are D. C. J. Biol. PubMed Scopus Google Scholar). the is of amino the a is present at are no amino with other mollusc of the sequence a molecular of the on the native nerve globin a molecular of which the of the and is not as is of the most in on of the different of proteins but on proteins Proc. Sci. S. A. PubMed Scopus Google Scholar, B. F. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). We observed molecular and that from the native by and with a binding of a and a to the Their physiological however, is The the of with no however, molecular of the of a The binding of to native and S. solidissima nHb was by not of native S. solidissima of the the molecular was from S. solidissima and and from The nHb was by and and to observed sequence The sequence in the whereas only in the were We and in the in from to The of the S. solidissima nHb is on of and from the and the the from the The and and they are at the and of the in B of the and The of the and is a of vertebrate many globin The S. solidissima nHb does not a within the which is for the in vertebrates and (1Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar, B. Burmester T. Hankeln T. Biol. PubMed Scopus Google Scholar, A. Fuchs C. Hankeln T. Burmester T. Biol. 2005; PubMed Scopus Google Scholar). and of the of S. solidissima nHb a at The and in the are found at and as reported by and PubMed Scopus Google Scholar). were observed for the of Hb Weber R.E. Dewilde S. Wittenberg J.B. Wittenberg B.A. Van Hauwaert M.L. Moens L. 2000; PubMed Scopus Google Scholar) and E. M. and in Their with Scholar). For the is to a which is in with the of the of Hb Weber R.E. Dewilde S. Wittenberg J.B. Wittenberg B.A. Van Hauwaert M.L. Moens L. 2000; PubMed Scopus Google Scholar). The and of are at and in with the of Hb Weber R.E. Dewilde S. Wittenberg J.B. Wittenberg B.A. Van Hauwaert M.L. Moens L. 2000; PubMed Scopus Google Scholar). In the of Spisula nHb the at The and at and were also found for Hb Wittenberg J.B. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), Hb R. J. Physiol. PubMed Scopus Google Scholar), S. Kiger L. Burmester T. Hankeln T. T. Marden M.C. R. Moens L. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar), and N. S. PubMed Scopus Google Scholar). The are for low heme with a of the iron The amino sequence of S. solidissima nHb that the sixth of the iron in the is most likely The of nHb, and are shown in is that the and in the high of the are to the and of the iron at the of the heme In the of and and are at and in with on heme proteins in the the of Hb Weber R.E. Dewilde S. Wittenberg J.B. Wittenberg B.A. Van Hauwaert M.L. Moens L. 2000; PubMed Scopus Google Scholar). of the to a The of this is at and which with the of the is by the of nHb, with and and are at and for a hexacoordinate low heme the a high is as is by the at and that the of the is lower than the of the that is only a as the of is high for species in with species. has been found for other M. Burmester T. Hankeln T. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). In the of S. solidissima and are at and for a low the at and that is a of which with a of be with the at and with this at The first was observed in D. PubMed Scopus Google Scholar). In Mb, this at low of the heme is to of the heme with a and the surrounding amino The was also observed in D. PubMed Scopus Google Scholar) and N. S. PubMed Scopus Google Scholar) and was to a in which the heme is to the of by that no at are in to several other heme proteins of a of the heme iron, such as M. Burmester T. Hankeln T. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar), N. S. PubMed Scopus Google Scholar), or Hb J. Wittenberg B.A. Wittenberg J.B. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). to a of to with several surrounding amino The at be to the that the is which is for of the heme was shown that the of the heme for O2 and binding Weber R.E. Dewilde S. Wittenberg J.B. Wittenberg B.A. Van Hauwaert M.L. Moens L. 2000; PubMed Scopus Google Scholar). has been shown that the is to with the oxygen of the heme is as the O2 A. C. Dewilde S. Moens L. Weber R.E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Kinetic and of to and S. solidissima the oxygen equilibrium for S. solidissima nHb at and the expressed as a these the oxygen affinity is with a of ∼0.6 and oxygen is in a as by a of in the The and found in on the are lower than reported from in measurements on nerves at high a of and of were found D.W. Doeller J.E. Biol. Bull. 1988; 174: Google Scholar). The in and measurements were in on a whereas the to the native in in at high and/or the of in that lower oxygen of the native but not the also to the observed M. D. S. J. A. J. PubMed Scopus Google Scholar) that a Hb is characterized by the of the by that is in a oxygen show for of S. solidissima of is the of binding of as observed for other hexacoordinate such as vertebrate or S. Kiger L. Burmester T. Hankeln T. T. Marden M.C. R. Moens L. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, A. Bolognesi M. A. Dewilde S. Moens L. Hankeln T. Burmester T. PubMed Scopus Google Scholar). In the of the S. solidissima nHb the of the is as the for binding is only as with for of The binding for and oxygen are high with oxygen the as observed for heme The for oxygen is the the for the globin binding solidissima in a The histidine is of than that observed for other are few for of the histidine only with for is S. Kiger L. Burmester T. Hankeln T. T. Marden M.C. R. Moens L. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, A. Bolognesi M. A. Dewilde S. Moens L. Hankeln T. Burmester T. PubMed Scopus Google Scholar). The in in a binding of for the of S. solidissima of these for is with the binding and the are than for the of In the of Ngb, is of on the D. Kiger L. Dewilde S. A. J. Burmester T. Hankeln T. Bolognesi M. Moens L. Marden M.C. PubMed Scopus Google Scholar), which be by of to the was no effect of the on the S. solidissima nHb binding was as the present (in and are to a The O2 affinity from the torr) is in with the by equilibrium measurements be of the in the the oxygen binding from the of the affinity We conclude from the and binding that S. solidissima nHb be as intracellular hemoglobin a function. The is the nature of the iron The and however, vertebrate Hb and Mb, their of a of their heme J. Biochem. J. PubMed Scopus Google Scholar, I. S. PubMed Scopus Google Scholar, J. I. J. Biol. Chem. Full Text PDF PubMed Google Scholar). of high pressure to Hbs also the of in a of binding D. Kiger L. Dewilde S. J. Burmester T. Hankeln T. Moens L. Marden M.C. J. Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). Phylogenetic amino sequence of the S. solidissima nHb has of only and a the of to vertebrate and In amino and to other mollusc Hbs and The amino sequence of the nHb was to of vertebrate and invertebrate globin (1Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar, T. Ebner B. Weich B. Hankeln T. Biol. PubMed Scopus Google Scholar, B. Burmester T. Hankeln T. Biol. PubMed Scopus Google Scholar), mollusc Phylogenetic were the and the were as of the the S. solidissima nHb a with the mollusc Hbs and with the Hbs of the bivalve mollusc L. Hbs are to supply O2 and or for a in the of these and R.E. Vinogradov S.N. Physiol. Rev. 2001; 81: 569-628Crossref PubMed Scopus (414) Google Scholar). In to the S. solidissima nHb, the nHb of the annelid A. aculeata (6Dewilde S. Blaxter M. Van Hauwaert M.L. Vanfleteren J. Esmans E.L. Marden M. Griffon N. Moens L. J. Biol. Chem. 1996; 271: 19865-19870Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar) with vertebrate as (1Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar). The and nHb sequence from the nemertean worm C. lacteus (7Vandergon T.L. Riggs C.K. Gorr T.A. Colacino J.M. Riggs A.F. J. Biol. Chem. 1998; : 16998-17011Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar) to at to the and was therefore from the not is most likely on of the globin than on (7Vandergon T.L. Riggs C.K. Gorr T.A. Colacino J.M. Riggs A.F. J. Biol. Chem. 1998; : 16998-17011Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar). for and nervous system of vertebrates and invertebrates of and is therefore not that neurons are to in oxygen supply as (e.g. or J.M. M.C. D.W. J. 2000; PubMed Scopus Google Scholar). is no that proteins that enhance oxygen or oxygen for be for the of neurons and are found in the nervous of invertebrate (4Wittenberg J.B. Advances in Comparative and Environmental Physiology.in: Mangum C.P. Springer-Verlag Berlin, Heidelberg1992: 59-85Google Scholar). glial nHbs the in the bivalve mollusc S. solidissima are present in species that hypoxia in their (4Wittenberg J.B. Advances in Comparative and Environmental Physiology.in: Mangum C.P. Springer-Verlag Berlin, Heidelberg1992: 59-85Google Scholar, 5Weber R.E. Vinogradov S.N. Physiol. Rev. 2001; 81: 569-628Crossref PubMed Scopus (414) Google Scholar). have that glial nHbs these to function in (9Kraus D.W. Colacino J.M. Science. 1986; 232: 90-92Crossref PubMed Scopus (43) Google Scholar, J.E. D.W. Biol. Bull. 1988; 174: PubMed Google Scholar). of the S. solidissima nHb is in with the proposed O2 supply by the O2 affinity of this are, however, of the S. solidissima nHb iron the of which in the nHb function are not had been proposed that invertebrate nHbs are to vertebrate (1Burmester T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google Scholar). was on the that in the nHb of the annelid A. aculeata with and T. Weich B. Reinhardt S. Hankeln T. Nature. 2000; 407: 520-523Crossref PubMed Scopus (905) Google and this have shown that the nHb of the bivalve mollusc S. solidissima does not to the A. aculeata but with the other mollusc Hbs and demonstrates that a Hb or has been during to fulfill the of O2 to the nerve cells of S. nHbs are therefore of mollusc glial nHbs have only as a for the function of in the nervous system of vertebrates (2Hankeln T. Ebner B. Fuchs C. Gerlach F. Haberkamp M. Laufs T.L. Roesner A. Schmidt M. Weich B. Wystub S. Saaler-Reinhardt S. Reuss S. Bolognesi M. de Sanctis D. Marden M.C. Kiger L. Moens L. Dewilde S. Nevo E. Avivi A. Weber R.E. Fago A. Burmester T. J. Inorg. Biochem. 2005; 99: 110-119Crossref PubMed Scopus (258) Google Scholar). We however, that expressed to a expression have been for air-breathing gastropod (11Schindelmeiser I. Kuhlmann D. Nolte A. Comp. Biochem. Physiol. B. 1979; 64B: 149-154Crossref Scopus (11) Google Scholar), which most vertebrates not of a nHb is a to vertebrate therefore be to the and cellular function of invertebrate nHbs in with the invertebrate glial nHbs and vertebrate of Hb a is that the S. solidissima nHb the first Hb to be found in in this the vertebrate proteins S. Kiger L. Burmester T. Hankeln T. T. Marden M.C. R. Moens L. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, A. Dewilde S. M. Moens L. Hankeln T. Burmester T. Bolognesi M. Full Text Full Text PDF PubMed Scopus Google Scholar). that a hexacoordinate heme has in globin A. Fuchs C. Hankeln T. Burmester T. Biol. 2005; PubMed Scopus Google Scholar). The S. solidissima nHb be as a in the of this is for the with of the Spisula nerve with
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