RESUMO
Mya truncata, a soft shell clam, is presented as a new model to study biomineralization through a proteomics approach. In this study, the shell and mantle tissue were analysed in order to retrieve knowledge about the secretion of shell matrix proteins (SMPs). Out of 67 and 127 shell and mantle proteins respectively, 16 were found in both shell and mantle. Bioinformatic analysis of SMP sequences for domain prediction revealed the presence of several new domains such as fucolectin tachylectin-4 pentraxin-1 (FTP), scavenger receptor, alpha-2-macroglobulin (α2 M), lipocalin and myosin tail along with previously reported SMP domains such as chitinase, carbonic anhydrase, tyrosinase, sushi, and chitin binding. Interestingly, these newly predicted domains are attributed with molecular functions other than biomineralization. These findings suggest that shells may not only act as protective armour from predatory action, but could also actively be related to other functions such as immunity. In this context, the roles of SMPs in biomineralization need to be looked in a new perspective.
Assuntos
Exoesqueleto/crescimento & desenvolvimento , Mya/genética , Proteoma , Exoesqueleto/metabolismo , Animais , Calcificação Fisiológica , Mya/crescimento & desenvolvimento , Mya/metabolismo , Proteômica , EscóciaRESUMO
The objective of this work was to analyze oxidative metabolism in Mya arenaria. Total Fe content in M. arenaria collected in the German Wadden Sea was 1.9+/-0.7, 0.7+/-0.1 and 0.17+/-0.01 nmol/mg fresh weight (FW), in digestive glands (DG), mantle and gills, respectively. Labile Fe pool, assessed by electronic paramagnetic resonance (EPR), was 146+/-10 pmol/mg FW, and by the fluorescence method employing calcein it was 118+/-9 pmol/mg FW. The lipid radical content in the DG, assessed by EPR, was 27+/-7 pmol/mg FW, and the thiobarbituric reactive substances content amounted to 57+/-8 pmol/mg FW. Ascorbyl radical (A) content, assessed by quantification of EPR signals, was 0.04+/-0.01 pmol/mg FW, and the ascorbate content (AH(-)) was 478+/-12 pmol/mg FW. The ratio A/AH(-) was (8+/-1)x10(-5)AU, suggesting a minimum oxidative stress even under physiological conditions, presumably depending on basal metabolic functions. The content of nitric oxide (NO), assessed by EPR, was 99+/-3 pmol/mg FW. The generation rate of NO by nitric oxide synthase-like activity (NOS-like) was assayed as NO production detected by EPR in the presence of l-arginine and NADPH, and was 3.16+/-0.06 pmol/(mg FW min). The data presented here document the detectable presence of highly reactive species in M. arenaria.