0000000001035044
AUTHOR
James H. Marden
Diversity of stonefly hexamerins and implication for the evolution of insect storage proteins
Hexamerins are large storage proteins of insects in the 500 kDa range that evolved from the copper-containing hemocyanins. Hexamerins have been found at high concentration in the hemolymph of many insect taxa, but have remained unstudied in relatively basal taxa. To obtain more detailed insight about early hexamerin evolution, we have studied hexamerins in stoneflies (Plecoptera). Stoneflies are also the only insects for which a functional hemocyanin is known to co-occur with hexamerins in the hemolymph. Here, we identified hexamerins in five plecopteran species and obtained partial cDNA sequences from Perla marginata (Perlidae), Nemoura sp. (Nemouridae), Taeniopteryx burksi (Taeniopterygid…
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 pressu…