Structural and functional characterization of <Emphasis Type="Italic">Delphinus delphis</Emphasis> hemoglobin system |
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Authors: | Barbara Manconi Irene Messana Federica Maggiani Alessandra Olianas Mariagiuseppina Pellegrini Roberto Crnjar Massimo Castagnola Bruno Giardina Maria Teresa Sanna |
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Institution: | (1) Department of Applied Sciences to Biosystems, University of Cagliari, Cittadella Universitaria, 09042 Monserrato (CA), Italy;(2) Department of Experimental Biology, University of Cagliari, Cittadella Universitaria, 09042 Monserrato (CA), Italy;(3) Institute of Biochemistry and Clinical Chemistry, Catholic University, Largo F. Vito, 1, 00168 Rome, Italy;(4) Institute of Chemistry of Molecular Recognition, CNR, Largo F. Vito, 1, 00168 Rome, Italy; |
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Abstract: | Structural analysis of the hemoglobin (Hb) system of Delphinus delphis revealed a high globin multiplicity: HPLC–electrospray ionization-mass spectrometry (ESI-MS) analysis evidenced three major
β (β1 16,022 Da, β2 16,036 Da, β3 16,036 Da, labeled according to their progressive elution times) and two major α globins
(α1 15,345 Da, α2 15,329 Da). ESI-tandem mass and nucleotide sequence analyses showed that β2 globin differs from β1 for the
substitution Val126 → Leu, while β3 globin differs from β2 for the isobaric substitution Lys65 → Gln. The α2 globin differs
from the α1 for the substitution Ser15 → Ala. Anion-exchange chromatography allowed the separation of two Hb fractions and
HPLC–ESI-MS analysis revealed that the fraction with higher pI (HbI) contained β1, β2 and both the α globins, and the fraction with lower pI (HbII) contained β3 and both the α globins. Both D. delphis Hb fractions displayed a lower intrinsic oxygen affinity, a decreased effect of 2,3-BPG and a reduced cooperativity with
respect to human HbA0, with HbII showing the more pronounced differences. With respect to HbA0, either the substitution Proβ5 → Gly or the Proβ5 → Ala is present in all the cetacean β globins sequenced so far, and it
has been hypothesized that position 5 of β globins may have a role in the interaction with 2,3-BPG. Regarding the particularly
lowered cooperativity of HbII, it is interesting to observe that the variant human HbA, characterized by the substitution
Lysβ65 → Gln (HbJ-Cairo) has a decreased cooperativity with respect to HbA0. |
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