Synthesis and secretion of a precursor hemolymph juvenile hormone-binding protein in the adult female cockroach Leucophaea maderae |
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| Affiliation: | 1. GRECO, Institute of Aquatic Ecology, Faculty of Sciences, Universitat de Girona, Girona, Spain;2. FEHM-Lab (Freshwater Ecology, Hydrology and Management), Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Facultat de Biologia, Universitat de Barcelona (UB), Barcelona, Catalonia/Spain;3. Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona (UB), Barcelona, Catalonia/Spain;4. Department of Evolutionary Biology, Ecology and Environmental Sciences, Universitat de Barcelona, Barcelona, Spain;5. WasserCluster Lunz—Biologische Station GmbH, Lunz am See, Austria;6. Departamento de Ecología y Gestión Ambiental, Centro Universitario Regional del Este (CURE), Universidad de la República, Tacuarembó s/n, Maldonado, Uruguay;7. Institute of Environmental Assessment and Water Research (IDAEA), Spanish National Research Council (CSIC), Jordi Girona, Barcelona, Spain;1. CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France;2. Faculté des Sciences de la Vie, Université de Strasbourg, Strasbourg, France;1. Department of Biological Sciences, Western Illinois University, Macomb, IL 61455, USA;2. Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA;1. State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China;2. National Research Center of Geoanalysis, Beijing 100037, China |
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| Abstract: | Hemolymph juvenile hormone-binding protein (JHBP) is synthesized and secreted from fat body in the adult female cockroach, Leucophaea maderae. The data in this paper suggest it is initially secreted from the fat body as a larger peptide whereas data in the accompanying paper demonstrate that JHBP is apolipophorin I. Using media from cultures of fat body maintained in vitro, a JH-binding component was found that is JH III saturable, has a KD of 1.5 × 10−8 M, binds JH III > JH II > JH I, and has a sedimentation value of 6.5S on high salt sucrose gradients. Each of these properties is identical to those of the JHBP extracted from the hemolymph. To identify the protein that bound JH, media proteins were photoaffinity labeled with 10-[10,11-3H]epoxyfarnesyl diazoacetate ([3H]EFDA). The results revealed that two media proteins bound [3H]EFDA in the absence of JH III, but not in the presence of 100-fold excess JH III. The molecular weights of the two media peptides were estimated by SDS-PAGE to be 275,000 and 220,000.To determine if the JHBP found in media of fat body cultures was due to hemolymph contamination of fat body, incorporation of [3H]leucine into newly synthesized and secreted fat body proteins during a 48 h culture period was monitored. During the culture period, linear increases in the concentrations of radiolabeled 275 and 220 kD JHBP were observed. Monoclonal antibodies specific for the 220 kD hemolymph JHBP were found to recognize both the 275 and 220 kD JHBPs in the media.To investigate the possibility that the 275 kD protein is a precursor to the 220 kD protein and that components of the hemolymph process or modify the precursor, hemolymph was introduced into fat body cultures and relative concentrations of the 275 and 220 kD media JHBPs were determined. Addition of hemolymph to these organ cultures resulted in an increase in the concentration of radiolabeled 220 kD JHBP and a proportional decrease in the concentration of radiolabeled 275 kD JHBP, suggesting that the 275 kD protein is a precursor to the 220 kD hemolymph JHBP. The mechanism of processing or modification remains undetermined. |
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