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Fleas.

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Animals↗

Erythrocruorin from the water-flea Daphnia magna. Quaternary structure and arrangement of subunits.

The subunit structure of erythrocruorin from the cladoceran Daphnia magna was studied. The native protein was found to have a sedimentation coefficient (S2(20), w) of 17.9 +/- 0.2 S and a molecular weight, as determined by sedimentation equilibrium, of 494 000 +/- 33 000. Iron and haem determinations gave 0.312 +/- 0.011% and 3.84 +/- 0.04%, corresponding to minimal molecular weights of 17900 +/- 600 and 16 100 +/- 200 respectively. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis gave one band with mobility corresponding to a molecular weight of 31 000 +/- 1 500. The molecular weight of the polypeptide chain determined by sedimentation equilibrium in 6 M-guanidinium chloride and 0.1 M-2-mercaptoethanol is 31 100 +/- 1300. On a molecular-weight basis, Daphnia erythrocruorin is composed of 16 identical polypeptide chains carrying two haem groups each. The native structure is stable between pH5 and 8.5. At alkaline and acidic pH, a gradual decrease in the sedimentation coefficient down to 9.8S occurs. Above pH 10 and below pH4, a slow component with S20, w between 2.7S and 4.0S is observed. The 2.7S, 4.0S and 9.8S species are identified as single-chain subunits, subunit dimers and half-molecules respectively. We propose a model for the molecule composed of 16 2.7S subunits grouped in two layers stacked in an eclipsed orientation, the eight subunits of each layer occupying the vertices of a regular eight-sided polygon. Support for this arrangement is provided from electron microscopy and from analysis of the pH-dissociation pattern.

Animals↗

Cloning of a family of serine protease genes from the cat flea Ctenocephalides felis.

Serine protease gene fragments approximately 480 nucleotides in length were amplified from Ctenocephalides felis larval and adult cDNA libraries using degenerate oligonucleotide PCR primers. Partial clones of thirty-eight distinct serine protease encoding sequences were isolated, and nineteen different full-length cDNAs encoding mature serine proteases were subsequently cloned and sequenced. All of the mature proteases contained the histidine, aspartic acid and serine amino acids of the catalytic triad characteristic of serine proteases. The mature C. felis serine proteases had amino acid sequences that were at most 29-53% identical to those known insect and arachnid serine proteases. Two of the C. felis gene sequences had similarity with the Drosophila melanogaster developmental genes snake and stubble. mRNA expression of selected serine protease genes was examined in different life stages, tissues, genders, and in response to bloodfeeding.

Amino Acid Sequence↗

[Macrostylophora kinabaluae n. sp. (Insecta: Siphonaptera: Ceratophyllidae), a new flea from Sabah (Borneo, Eastern Malaysia)].

This species, known only by a single male, is described from Mount Kinabalu and thus is recorded from the same area as Macrostylophora borneensis (Jordan, 1926), teste Traub (1972). It is distinguished from its congeneric and characterized by the absence of eriged setae on the thorax and first abdominal tergits, as well as by the shape of terminal segments and the phallosom. Macrostylophora kinabaluae was found to parasitize the Sciurid rodent Callosciurus prevostii that is widespread throughout most areas in the Malaysian subregion.

Animals↗