HR: 0800h
AN: B21B-0879    [Abstracts]
TI: Effect of CaCO$_{3}$ Precipitation by the Organic Matrix of Sclerites Associated with Coccoliths and the Characterization of Proteinaceous Organic Matrices from the Alcyonarian, {\it Lobophytum Crassum}. (Octocorallia : Alcyoncea)
AU: * Rahman, M
EM: k038563@eve.u-ryukyu.ac.jp
AF: University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa, 903-0213 Japan
AU: Isa, Y
EM: isaeisin@sci.u-ryukyu.ac.jp
AF: University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa, 903-0213 Japan
AB: Many of the invertebrates possess calcium carbonate skeletal tissues. There is an organic matrix in the skeleton, which is supposed to provide a nucleating site for the CaCO$_{3}$ deposition and the determination of crystal forms (calcite and/or aragonite). It is reported that the calcified organic substances in skeleton contain a protein-polysaccharide complex taking a key role in the regulation of bio\-calcification. However, information concerning the matrix proteins in alcyonarian and their effect on calcification process is still unknown. For this reason, we have studied the organic matrix of endoskeletal sclerites from alcyonarian coral, {\it Lobophytum crassum}, to analyze the sequences and functional properties of the proteins present. The separated sclerites from the colony were identified by scanning electron microscope (SEM). The soluble organic matrix comprised 0.04% of the sclerites weight. By recording the decline of pH in the experimental design, the inhibitory effect of the matrix on CaCO$_{3}$ precipitate was revealed. SDS-PAGE analysis of the preparations showed four bands of proteins with apparent molecular weights of 102, 67, 48 and 37 kDa. The proteins were transferred to polyvinylidene difluoride (PVDF) membranes and their N-termini were sequenced. A major band of about 67 kDa protein was determined the N-terminal amino acid sequence. The calcium-binding soluble proteins, which are responsible for calcium carbonate nucleation and crystal growth, were detected as radioactive bands by $^{45}$Ca autoradiography. The 102 and 67 kDa calcium-binding proteins were found to be radioactive. Periodic acid schiff staining indicated the 67 kDa protein was glycosylated. A carbonic anhydrase, which is thought to be play an important role in the process of calcification, revealed low level of activity. These findings suggest that the endoskeletal sclerites of alcyonarian corals have protein-rich organic matrices, which might be related to the calcification process.
DE: 1800 HYDROLOGY
DE: 1845 Limnology
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting