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Proteomic identification of Drosophila melanogaster male accessory gland proteins, including a pro-cathepsin and a soluble gamma-glutamyl transpeptidase.

Walker, Michael J. and Rylett, Caroline M. and Keen, Jeffrey N. and Audsley, Neil and Sajid, Mohammed and Shirras, Alan D. and Isaac, R. Elwyn (2006) Proteomic identification of Drosophila melanogaster male accessory gland proteins, including a pro-cathepsin and a soluble gamma-glutamyl transpeptidase. Proteome Science, 4. p. 9. ISSN 1477-5956

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    Abstract

    Background In Drosophila melanogaster, the male seminal fluid contains proteins that are important for reproductive success. Many of these proteins are synthesised by the male accessory glands and are secreted into the accessory gland lumen, where they are stored until required. Previous studies on the identification of Drosophila accessory gland products have largely focused on characterisation of male-specific accessory gland cDNAs from D. melanogaster and, more recently, Drosophila simulans. In the present study, we have used a proteomics approach without any sex bias to identify proteins in D. melanogaster accessory gland secretions. Results Thirteen secreted accessory gland proteins, including seven new accessory gland proteins, were identified by 2D-gel electrophoresis combined with mass spectrometry of tryptic fragments. They included protein-folding and stress-response proteins, a hormone, a lipase, a serpin, a cysteine-rich protein and two peptidases, a pro-enzyme form of a cathepsin K-like cysteine peptidase and a γ-glutamyl transpeptidase. Enzymatic studies established that accessory gland secretions contain a cysteine peptidase zymogen that can be activated at low pH. This peptidase may have a role in the processing of female and other male-derived proteins, but is unlikely to be involved in the processing of the sex peptide. γ-Glutamyl transpeptidases are type II integral membrane proteins; however, the identified AG γ-glutamyl transpeptidase (GGT-1) is unusual in that it is predicted to be a soluble secreted protein, a prediction that is supported by biochemical evidence. GGT-1 is possibly involved in maintaining a protective redox environment for sperm. The strong γ-glutamyl transpeptidase activity found in the secretions provides an explanation for the observation that glutamic acid is the most abundant free amino acid in accessory gland secretions of D. melanogaster. Conclusion We have applied biochemical approaches, not used previously, to characterise prominent D. melanogaster accessory gland products. Of the thirteen accessory gland secreted proteins reported in this study, six were represented in a D. simulans male accessory gland EST library that was biased for male-specific genes. Therefore, the present study has identified seven new secreted accessory gland proteins, including GGT-1, which was not recognised previously as a secreted accessory gland product.

    Item Type: Article
    Journal or Publication Title: Proteome Science
    Subjects: Q Science > QH Natural history > QH301 Biology
    Departments: Faculty of Health and Medicine > Biomedical & Life Sciences
    Faculty of Science and Technology > Lancaster Environment Centre
    ID Code: 9400
    Deposited By: Dr Alan Shirras
    Deposited On: 09 Jun 2008 09:21
    Refereed?: Yes
    Published?: Published
    Last Modified: 26 Jul 2012 18:36
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/9400

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