Structure and function of the Gondwanian hemoglobin of Pseudaphritis urvillii, a primitive notothenioid fish of temperate latitudes.
The suborder Notothenioidei dominates the Antarctic ichthyofauna. The non-Antarctic monotypic family Pseudaphritidae is one of the most primitive families. The characterization of the oxygen-transport system of euryhaline Pseudaphritis urvillii is herewith reported. Similar to most Antarctic notothenioids, this temperate species has a single major hemoglobin (Hb 1, over 95% of the total). Hb 1 has strong Bohr and Root effects. It shows two very uncommon features in oxygen binding: At high pH values, the oxygen affinity is exceptionally high compared to other notothenioids, and subunit cooperativity is modulated by pH in an unusual way, namely the curve of the Hill coefficient is bell-shaped, with values approaching 1 at both extremes of pH. Molecular modeling, electronic absorption and resonance Raman spectra have been used to characterize the heme environment of Hb 1 in an attempt to explain these features, particularly in view of some potentially important nonconservative replacements found in the primary structure. Compared to human HbA, no major changes were found in the structure of the proximal cavity of the alpha-chain of Hb 1, although an altered distal histidyl and heme position was identified in the models of the beta-chain, possibly facilitated by a more open heme pocket due to reduced steric constraints on the vinyl substituent groups. This conformation may lead to the hemichrome form identified by spectroscopy in the Met state, which likely fulfils a potentially important physiological role.
Verde
Cinzia
C
Institute of Protein Biochemistry, National Research Council, Naples, Italy.
Howes
Barry D
BD
De Rosa
M Cristina
MC
Raiola
Luca
L
Smulevich
Giulietta
G
Williams
Richard
R
Giardina
Bruno
B
Parisi
Elio
E
Di Prisco
Guido
G
D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D006418:Heme / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010100:Oxygen / Q000378:metabolism; D010473:Perciformes; D010802:Phylogeny; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D006454:Hemoglobins; D006418:Heme; D010100:Oxygen