A respiratory hemocyanin from an insect.
Insects possess an elaborate tracheal system that enables transport of gaseous oxygen from the atmosphere directly to the inner organs. Therefore, the presence of specialized oxygen-transport proteins in the circulatory system of insects has been considered generally unnecessary. Here, we show for the first time, to our knowledge, the presence of an ancestral and functional hemocyanin (Hc) in an insect. In the hemolymph of nymphs and adults of the stonefly Perla marginata, a hexameric Hc was identified, which consists of two distinct subunit types of 659 and 655 amino acids. P. marginata Hc displays cooperative oxygen binding with a moderately high oxygen affinity [(half-saturation pressure, P(50) approximately 8 torr (1 torr = 133 Pa)]. No evidence was found for the presence of Hcs in the more evolutionarily advanced holometabolan insects, suggesting that this type of respiratory protein was lost later in insect evolution. However, our results demonstrate that, in contrast to the accepted paradigm, certain basal insects have retained an ancestral blood-based mechanism of gas exchange.
Hagner-Holler
Silke
S
Institutes of Zoology and Molecular Biophysics, Johannes Gutenberg University of Mainz, 55099 Mainz, Germany.
Schoen
Axel
A
Erker
Wolfgang
W
Marden
James H
JH
Rupprecht
Rainer
R
Decker
Heinz
H
Burmester
Thorsten
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003445:Crustacea / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D006433:Hemocyanins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D007313:Insecta / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010802:Phylogeny; D021122:Protein Subunits; D012119:Respiration; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D019476:Insect Proteins; D021122:Protein Subunits; D006433:Hemocyanins; D010100:Oxygen