Purificação e caracterização bioquímica de uma proteína relacionada a ependimina presente na esponja marinha Amphimedon compresa (Duchassaing & Michelotti, 1864)

Abstract

Ependimins are glycoproteins initially identified in teleost fish and associated with neuroplastic and regenerative functions. Recent studies, however, have revealed their presence in various organisms, including marine sponges, where they exhibit highly conserved characteristics and perform a range of functions. This work aimed to isolate and biochemically characterize an ependimin-related protein (EPDR) extracted from the sponge Amphimedon compresa. To achieve this, a protocol was employed that involved the extraction of biological material, fractionation by ammonium sulfate precipitation, ion exchange chromatography onDEAE-Sephacel, and size exclusion chromatography, followed by analyses to estimate the protein’s molecular mass under denaturing conditions and in its native state by SDS-PAGE and size exclusion chromatography, respectively, as well as circular dichroism spectropolarimetry and LC-MS/MS sequencing. The purified protein, named AC-EPD, exhibited a mass of approximately 25 kDa under denaturing conditions and 57 kDa in its native state, suggesting the formation of dimers stabilized by non-covalent interactions. The circular dichroism spectra indicated a predominantly beta secondary structure; the protein is composed of % alpha helix, 42% beta sheets, 22% beta turns, and 32% loops, and had a melting temperature determined at 79.18ºC. Sequencing confirmed its relationship with ependimins from other species, particularly with two ependimins derived from marine sponges. These results demonstrate the efficiency of the adopted protocol and open prospects for the application of EPDRs as carriers of hydrophobic molecules, contributing to advances in the bioprospecting of natural resources in marine sponges.