Seminal plasma and sperm proteome of ring-tailed coatis (Nasua nasua, Linnaeus, 1766)

Abstract Ring-tailed coati is listed as a species of least concern in the International Union for Conservation of Nature (IUCN) Red List, however, there has been a sharp decline in their population. The present study was conducted to evaluate the major proteins of both seminal plasma and sperm in ring-tailed coatis. Semen sample was collected from three adult coatis and evaluated for their morphological characteristics. Further, the sample was centrifuged to separate spermatozoa from seminal plasma, and then stored in liquid nitrogen. The seminal plasma and sperm proteins were subjected to one-dimensional (1-D) sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and identified by mass spectrometry. Gene ontology and protein networks were analyzed using bioinformatics tools. Based on sperm concentration and average protein content of the semen, the concentration of protein/spermatozoon was found to be 104.69 ± 44.43 μg. The analysis of SDS-PAGE gels showed 20.3 ± 3.1 and 17 ± 2 protein bands/lane for seminal plasma and sperm, respectively. In-gel protein digestion and peptide analysis by mass spectrometry revealed 238 and 246 proteins in the seminal plasma and sperm, respectively. The gene ontology analysis revealed that the proteins of seminal plasma mainly participated in cellular (35%) and regulatory (21%) processes. According to their cellular localization, seminal plasma proteins were categorized as structural (18%), extracellular (17%), and nuclear (14%) proteins with molecular functions, such as catalytic activity (43%) and binding (43%). The sperm proteins were also involved in cellular (38%) and regulatory (23%) processes, and mainly categorized as extracellular (17%), nuclear (13%), and cytoplasmic (10%) proteins. The major molecular functions of the sperm proteins were catalytic activity (44%) and binding (42%). These results indicated that the seminal plasma of ring-tailed coati has an array of proteins that can potentially modulate several sperm functions, from sperm protection to oocyte binding. However, further studies are necessary to interpret the roles of these major seminal plasma proteins in coatis.