TY - JOUR
T1 - Evolution of the sulfide-binding function within the globin multigenic family of the deep-sea hydrothermal vent tubeworm Riftia pachyptila
AU - Bailly, Xavier
AU - Jollivet, Didier
AU - Vanin, Stephano
AU - Deutsch, Jean
AU - Zal, Franck
AU - Lallier, Franfois
AU - Toulmond, André
PY - 2002/9/1
Y1 - 2002/9/1
N2 - The giant extracellular hexagonal bilayer hemoglobin (HBL-Hb) of the deep-sea hydrothermal vent tube worm Riftia pachyptita is able to transport simultaneously O2 and H2S in the blood from the gills to a specific organ' the trophosome that harbors sulfide-oxidizing endosymbionts. This vascular HBL-Hb is made of 144 globins from which four globin types (A1, A2, B1, and B2) coevolve. The H2S is bound at a specific location (not on the heme site) onto two of these globin types. In order to understand how such a function emerged and evolved in vestimentiferans and other related annelids, six partial cDNAs corresponding to the six globins known to compose the multigenic family of R. pachyptila have been identified and sequenced. These partial sequences (ca. 120 amino acids, i.e., 80% of the entire protein) were used to reconstruct molecular phylogenies in order to trace duplication events that have led to the family organization of these globins and to locate the position of the free cysteine residues known to bind H2S. From these sequences, only two free cysteine residues have been found to occur, at positions Cys + 1 (i.e., 1 a.a. from the well-conserved distal histidine) and Cys + 11 (i.e., 11 a.a. from the same histidine) in globins B2 and A2, respectively. These two positions are well conserved in annelids, vestimentiferans, and pogonophorans, which live in sulfidic environments. The structural comparison of the hydrophobic environment that surrounds these cysteine residues (the sulfide-binding domain) using hydrophobic cluster analysis plots, together with the cysteine positions in paralogous strains, suggests that the sulfide-binding function might have emerged before the annelid radiation in order to detoxify this toxic compound. Moreover, globin evolutionary rates are highly different between paralogous strains. This suggests that either the two globin subfamilies involved in the sulfidebinding function (A2 and B2) have evolved under strong directional selective constraints (negative selection) and that the two other globins (A1 and B1) have accumulated more substitutions through positive selection or have evolved neutrally after a relaxation of selection pressures. A likely scenario on the evolution of this multigenic family is proposed and discussed from this data set.
AB - The giant extracellular hexagonal bilayer hemoglobin (HBL-Hb) of the deep-sea hydrothermal vent tube worm Riftia pachyptita is able to transport simultaneously O2 and H2S in the blood from the gills to a specific organ' the trophosome that harbors sulfide-oxidizing endosymbionts. This vascular HBL-Hb is made of 144 globins from which four globin types (A1, A2, B1, and B2) coevolve. The H2S is bound at a specific location (not on the heme site) onto two of these globin types. In order to understand how such a function emerged and evolved in vestimentiferans and other related annelids, six partial cDNAs corresponding to the six globins known to compose the multigenic family of R. pachyptila have been identified and sequenced. These partial sequences (ca. 120 amino acids, i.e., 80% of the entire protein) were used to reconstruct molecular phylogenies in order to trace duplication events that have led to the family organization of these globins and to locate the position of the free cysteine residues known to bind H2S. From these sequences, only two free cysteine residues have been found to occur, at positions Cys + 1 (i.e., 1 a.a. from the well-conserved distal histidine) and Cys + 11 (i.e., 11 a.a. from the same histidine) in globins B2 and A2, respectively. These two positions are well conserved in annelids, vestimentiferans, and pogonophorans, which live in sulfidic environments. The structural comparison of the hydrophobic environment that surrounds these cysteine residues (the sulfide-binding domain) using hydrophobic cluster analysis plots, together with the cysteine positions in paralogous strains, suggests that the sulfide-binding function might have emerged before the annelid radiation in order to detoxify this toxic compound. Moreover, globin evolutionary rates are highly different between paralogous strains. This suggests that either the two globin subfamilies involved in the sulfidebinding function (A2 and B2) have evolved under strong directional selective constraints (negative selection) and that the two other globins (A1 and B1) have accumulated more substitutions through positive selection or have evolved neutrally after a relaxation of selection pressures. A likely scenario on the evolution of this multigenic family is proposed and discussed from this data set.
KW - Duplication
KW - HS
KW - Hexagonal bilayer hemoglobin
KW - Riftia pachyptila
KW - Selection
KW - Sulfide-binding domain
UR - http://www.scopus.com/inward/record.url?scp=0036728906&partnerID=8YFLogxK
U2 - 10.1093/oxfordjournals.molbev.a004205
DO - 10.1093/oxfordjournals.molbev.a004205
M3 - Article
C2 - 12200470
AN - SCOPUS:0036728906
VL - 19
SP - 1421
EP - 1433
JO - Molecular Biology and Evolution
JF - Molecular Biology and Evolution
SN - 0737-4038
IS - 9
ER -