Alterations in the properties of sperm protamine-like II protein after exposure of Mytilus galloprovincialis (Lamarck 1819) to sub-toxic doses of cadmium.

Abstract Protamine-like proteins (PL-II, PL-III and PL-IV) represent the major basic nuclear component of Mytilus galloprovincialis L sperm chromatin. The present study investigates the effects induced on the properties of PL-II protein after exposure of Mytilus galloprovincialis L for 24 h to 1.5 and 5 µM CdCl 2. We found cadmium accumulation in protamine-like proteins with a linear grow up with the exposition dose. In particular, after 5 µM CdCl 2 mussels exposure, the mobility of PL-II band changed in SDS-PAGE, suggesting structural rearrangement in presence of cadmium. Structural analysis using fluorescent probes, indicated that at 5 µM CdCl 2 the complete conformational change of PL-II protein was reached. In the same condition of mussels exposure of 5 µM CdCl 2 , PL-II protein changed its DNA binding mode, which determined a closer DNA binding, because higher amount of NaCl were required for PL-II protein release by sperm nuclei. These results supported the hypothesis that mussel exposure to this CdCl 2 dose, although lower to toxic ones, affects the properties of this protein and as a consequence chromatin organization of spermatozoa that is essential for the success of fertilization. Highlights • Mytilus galloprovincialis L. is an usefull model organism for heavy metals biomonitoring. • Cadmium accumulates in protamine-like proteins. • 5 µM CdCl 2 mussels exposure produces protamine-like-II protein conformational changes. • 5 µM CdCl 2 mussels exposure changes protamine-like-II protein DNA binding mode. [ABSTRACT FROM AUTHOR]