Alkaline Bohr effect of bird hemoglobins: the case of the flamingo.
The hemoglobin (Hb) substitution His-->Gln at position alpha89, very common in avian Hbs, is considered to be responsible for the weak Bohr effect of avian Hbs. Phoenicopterus ruber ruber is one of the few avian Hbs that possesses His at alpha89, but it has not been functionally characterized yet. In the present study the Hb system of the greater flamingo (P. ruber roseus), a bird that lives in Mediterranean areas, has been investigated to obtain further insight into the role played by the alpha89 residue in determining the strong reduction of the Bohr effect. Functional analysis of the two purified Hb components (HbA and HbD) of P. ruber roseus showed that both are characterized by high oxygen affinity in the absence of organic phosphates, a strong modulating effect of inositol hexaphosphate, and a reduced Bohr effect. Indeed, in spite of the close phylogenetic relationship between the two flamingo species, structural analysis based on tandem mass spectrometry of the alpha(A) chain of P. ruber roseus Hb showed that a Gln residue is present at position alpha89.
Sanna
Maria Teresa
MT
Department of Applied Sciences in Biosystems, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy. sanna@unica.it
Manconi
Barbara
B
Podda
Gabriella
G
Olianas
Alessandra
A
Pellegrini
Mariagiuseppina
M
Castagnola
Massimo
M
Messana
Irene
I
Giardina
Bruno
B
D000595:Amino Acid Sequence; D000818:Animals; D001717:Birds / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D006454:Hemoglobins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010833:Phytic Acid / Q000494:pharmacology; D021241:Spectrometry, Mass, Electrospray Ionization; D013696:Temperature; D014357:Trypsin / Q000378:metabolism
D002712:Chlorides; D006454:Hemoglobins; D010455:Peptides; D010833:Phytic Acid; D014357:Trypsin; D010100:Oxygen