Figure 4. Isolation and identification of S-nitrosoproteins in human spermatozoa.

Biotinylated sperm proteins obtained from the biotin switch assay were purified by affinity chromatography using streptavidin-agarose and eluted with sample buffer containing DTT as described in Materials and Methods. Proteins were separated by SDS-PAGE (10%) and visualized by silver staining. The relative masses of protein standards are shown on the left. Individual bands were trypsinised and submitted to MS/MS for protein identification. More than 1 protein was found for each bands (see Table 1). Results of 1 experiment are representative of 5 others performed with different pools of sperm donors. Proteins shown on the right side of the gel are a sample of known sperm proteins that are shown in Table 1.