Isolation and partial characterization of the outer dense fiber proteins from human spermatozoa

Flagella of human spermatozoa were separated from the sperm head by sonication at 25 kHz and subsequent density gradient centrifugation in Percoll. For isolation of the outer dense fibers (ODF), the flagellar membrane and fibrous sheath were dissolved under reducing conditions in the cationic detergent cetyltrimethylammonium bromide (CTAB) for 30, 60 and 90 min, respectively. The isolation steps were monitored by phase-contrast microscopy and electron microscopy. After SDS-PAGE and silver staining two protein bands at 55 and 67 kDa could be detected. An identification of these proteins as phosphoproteins, either with molybdate/methylgreen or rhodamine B, was not possible. The obtained results indicate that the ODF proteins might have more passive elastic than active function with respect to motility of spermatozoa.