Pheromones of the Scarabaeinae, II : composition of the pheromone disseminating carrier material secreted by male dung beetles of the genus Kheper
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Gel electrophoresis of the white flocculent pheromone disseminating secretions produced by males of the three dung beetle species, Kheper lumarcki, K. nigroacneus and K. subaeneus, revealed that three different proteins with molecular masses of ca. 15 kDa are the major constituents of these secretions. The molecular mass of these components in the secretions of K. lamarcki and K. nigroaeneus was determined more accurately by 252Cf plasma desorption mass spectrometry to be 15451 ± 10 and 15477± 10 Da respectively. The N-terminal amino acids in the major proteinaceous component of the secretions revealed similarities as well as differences in the primary structures of the proteins secreted by the three species. The amino acid composition of the secretions of the three species is closely related. Due to the presence of large amounts of aspartic and glutamic acid, and small amounts of the basic amino acids, the proteinaceous component of the carrier material is expected to have a low isoelectric point which, together with the presence of large amounts of the hydrophobic amino acids, may impart properties that are to be expected for a carrier material which is used for the dissemination of inter alia long-chain fatty acids and their esters. Exposure of bovine pancreas trypsin, bovine albumin and the carrier protein of K. lamarcki to the vapour of 2.6-dimethyl-5-heptenoic acid, the major volatile constituent with electroantennogram activity in the secretion of this species, followed by quantitative determination of the acid adsorbed on these proteins, showed that albumin and the carrier protein have an approximately equal affinity for the acid, whereas trypsin retained only about one third of the amount of the acid adsorbed on the other two proteins. lt was concluded that albumin should be a suitable substitute for the carrier protein in field tests with synthetic constituents of the abdominal secretion of these insects.