Abstracts - Deutsche Zoologische Gesellschaft

Physiology Symposium 85O PH.9 (Sa) - ENCryo TEM-based reconstruction of the recombinantly expressed human meprin betadimer, a zinc peptidase of the astacin familyPhilipp Arnold 1 , Arne Moeller 1 , Frank Depoix 1 , Christoph Becker-Pauly 2 , Walter Stöcker 2 , UlrichMeissner 11Institut für Zoologie, Abt. Molekulare Tierphysiologie, Johannes Gutenberg-Universität Mainz;2Institut für Zoologie, Abt. Zell- und Matrix-Biologie, Johannes Gutenberg-Universität MainzMeprins are astacin-type zinc peptidases distantly related to matrix metalloproteinases (MMPs)[Stöcker, W. and Bode, W. (1995) Curr Opin Struct Biol. 5, 383-390]. They are expressed in variousepithelia, intestinal leukocytes and cancer cells. They cleave basement membrane proteins, cytokinesand adhesion molecules, suggesting a role in epithelial differentiation, cell migration and immunereactions [Herzog, C.et al. (2005) Cytokine. 31, 394-403; Norman, L. P. et al. (2003) Mol Cell Biol.23, 1221-1230; Crisman, J. M. et al. (2004) J Immunol. 172, 4510-4519]. Although Meprin alphaand beta have an amino acid sequence identity of 44%, they show differences in activation, substratespecificity and quaternary structure. From negatively stained TEM it is known that meprin alphaforms ring- and chain shaped oligomers, up to mega Dalton size. This characterizes meprin alpha asthe largest known secreted protease [Becker, C. et al. (2003) Biol. Chem. 384, 825-831; Bertenshaw,G. P. et al. (2003) J. Biol. Chem. 278, 2522-2532]. In contrast meprin beta builds just homodimers.Here we present preliminary data of the quaternary structure of recombinant meprin beta homo dimersbased on cryo electron microscopy. We benefit from the pure soluble protein solution purifiedfrom insect cell (HiFive) supernatants [Kruse, M.-N. et al. (2004) Biochem J. 378, 383-389]. Thesmall size of the meprin beta dimer, appears as a challenge for a single particle analysis approach.O PH.10 (Sa) - ENThe hemocyanin of Caudofoveata: Implications on phylogeny and evolution in basalmollusksBernhard Lieb 1 , Rachel Brandl 1 , Christiane Todt 21Institut für Zoologie, Johannes Gutenberg Universität Mainz; 2 Department of Biology, Universityof Bergen, NorwayThe basal groups of mollusks are believed to encompass three major clades: Solenogastres, Caudofoveata,and Polyplacophora. The phylogenetic relationship between those clades is still a matter of debateand could not be resolved by analyzing commonly used molecular data. We started to investigate thisenigma by using hemocyanin sequences. Since it was not known whether solenogasters and caudofoveatesexpress hemocyanin at all, we collected a number of species of both groups from the Norwegianfjord region and performed hemocyanin expression studies. The results showed that only Caudofoveataexpress hemocyanin. Thus, it is not applicable to study relationships between the two clades ofaplacophoran mollusks but rather is one more character that separates them. Within the Caudofoveata,however, we were able to clone and obtain hemocyanin sequence data from three representative speciesto perform molecular-phylogenetic analyses: (i) the resulting trees reconstructed by Bayesian inferencesand by ML analyses showed a close relationship to other basal groups, such as Polyplacophora andNautilus pompilius, (ii) the intra-caudofoveate nodes show high bootstrap supports and significant PPvalues,and (iii) additionally, we could calculate and improve a molecular clock based on hemocyanindata providing evidence for the first emergence of Caudofoveata in a historical perspective, especiallyimportant considering the complete lack of fossil record for these shell-less mollusks.