Identification of storage-protein messenger RNA of the fleshfly Sarcophaga peregrina

The Musca domestica larval hexamerin is composed of multiple, similar polypeptides

The Musca domestica larval hexamerin (MdHex-L) is a hexameric glycoprotein with an apparent native molecular weight of 500 kDa. Seven different cDNAs that encode MdHex-L subunits were cloned and sequenced. Furthermore, amino acid sequences of isolated subunits were determined by the Edman degradation method and compared to the conceptual translation products derived from the cloned cDNAs. The obtained data indicate the existence of multiple forms of MdHex-L subunits and that these multiple forms may be grouped into three categories according to their percentages of nucleotide sequence identity.

Purification and cDNA cloning of the alcohol dehydrogenase of the flesh fly Sarcophaga peregrina. A structural relationship between alcohol dehydrogenase and a 25-kDa protein

We purified to homogeneity two proteins with molecular masses of 25 kDa from the fat body of the Sarcophaga larva. One was alcohol dehydrogenase (ADH) and the other was a 25-kDa protein of which the genomic DNA had been cloned. We isolated the cDNA for ADH and determined its amino acid sequence. Amino acid sequence identity between ADH and the 25-kDa protein was 40%, indicating that they are structurally related proteins. The amount of ADH in Sarcophaga was almost constant through the larval stage to the adult stage, but the 25-kDa protein was detected only within a restricted period between the final larval instar and the early pupal stage.

Molecular cloning and sequencing of arylphorin-binding protein in protein granules of the Sarcophaga fat body. Implications of a post-translational processing mechanism

Previously, we identified an arylphorin-binding protein of Sarcophaga peregrina (flesh fly) with a molecular mass of 120 kDa and suggested its participation in the selective uptake of arylphorin from the hemolymph into the pupal fat body at metamorphosis (Ueno, K., and Natori, S. (1984) J. Biol. Chem. 259, 12107-12111). This paper reports the isolation and sequencing of cDNA for the 120-kDa protein. This protein consists of 1146 amino acid residues. Immunoblotting and RNA blotting experiments revealed that this protein is present as two fragments of 76 kDa (695 residues) and 53 kDa (451 residues) in the larval fat body. When larvae pupate, the 120-kDa protein gene is further activated and the complete 120-kDa protein is synthesized without fragmentation. This suggests a novel mechanism for the production of the 120-kDa protein regulated by a proteinase depending upon the stage of development of Sarcophaga. All of these proteins were found to be localized in protein granules in the adipocytes.

Purification of Sarcophaga (fleshfly) lectin and detection of sarcotoxins in the culture medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina

An established cell line originating from a Sarcophaga peregrina (fleshfly) embryo, NIH-Sape-4, was found to synthesize mRNAs for Sarcophaga lectin and sarcotoxin IA, but not those for storage protein or 25 kDa protein. These four proteins are known to be synthesized in the fat-body of third-instar larvae, and the two former in particular are known to participate in the defence mechanism of this insect and to be induced in response to injury of the body wall. Thus the embryonic cell line NIH-Sape-4 synthesizes certain defence proteins constitutively. This cell line will be useful for large-scale purification of Sarcophaga lectin, since 50 micrograms of purified Sarcophaga lectin could be obtained from about 400 ml of culture medium.

Homologies of nucleotide sequences in the 5'-end regions of two developmentally regulated genes of Sarcophaga peregrina

In the previous paper we demonstrated that the storage protein gene and 25-kDa protein gene are expressed sequentially in the fat body of middle third-instar Sarcophaga peregrina larvae. In this paper, we showed that the expressions of these two genes are regulated at the transcriptional level, and searched for homologous nucleotide sequences in the two genes in the vicinity of their 5'-ends, assuming that these two genes are regulated by a common mechanism. We selected 9 homologous sequences and found that most of them were distributed in two clusters located between positions -400 and +1. We identified an SV40 enhancer core segment-like sequence in the nontranslated region of the first exons of both genes, which might explain the efficient transcriptions of these two genes.

Multi-gene structure of the storage protein genes of Sarcophaga peregrina

Three recombinant phages containing chromosomal segments of Sarcophaga peregrina encoding storage protein were isolated. These clones were found to contain sequences hybridized with the messenger RNA of 75,000 Mr protein, a monomer of storage protein. From restriction analysis it was found that message-homologous regions are not identical, and thus are different genes with similar sequences. From the analysis of these clones it was concluded that the storage protein gene belongs to a multi-gene family.

Differential expression of two abundant messenger RNAs during development of Sarcophaga peregrina

Expression of two abundant mRNAs in the fat body of third instar larvae of Sarcophaga peregrina was studied using genomic clones of storage protein and 25K protein as probes. It was found that these two genes were expressed sequentially in the third instar with a 20-hr interval between their expressions. No amplification of genes was detected during larval development, suggesting that the high level of mRNA was due to efficient transcription. The contents of the two mRNAs in third instar larvae were about the same, although the synthesis of storage protein was much more than that of 25K protein.