ISOLATION AND CHARACTERIZATION OF APOLIPOPHORIN-III FROM THE GIANT WATER BUG (LETHOCERUS-MEDIUS)

Upon injection of synthetic adipokinetic hormone, lipophorin from Leth ocerus medius decreased in ensity and became associated with apolipoph orin-III (apoLp-III), ApoLp-III isolated from hemolymph of Lethocerus medius had a M(r) = 19,000 and an amino acid composition high in methi onine, in comparison with other apoLp-IIIs. Its circular dichroism spe ctrum was consistent with a protein with secondary structure of predom inantly alpha-helix, NH2-terminal sequence alignment with apoLp-III se quences from other species showed a conservation of the hydrophobic or hydrophilic properties of residues at each position rather than of sp ecific amino acids, ApoLp-III from Lethocerus medius has the potential to form amphipathic alpha-helices, similar to those found in the thre e-dimensional structure of Locusta migratoria apoLp-III. A portion of the apoLp-III molecules that are not associated with lipophorin contai ned the blue chromophore, biliverdin.