OBJECTIVETo identify proteins in the seminal plasma of healthy fertile men.

METHODSThree seminal plasma samples were collected from healthy fertile volunteers by Percoll isolation, and then the balanced mixture of the seminal plasma was separated by SDS-PAGE. The proteins in the gel band underwent enzymoloysis, and was extracted and identified by shotgun proteomic strategy.

RESULTSA total of 331 proteins were identified, with the molecular weight (MW) ranging from 8 000 to 572 068 and the isoelectric point (pI) from 4.36 to 11.05. Based on the molecular function and biological process of the proteins, 51 (15.4%) were classified as transport proteins, 11 (3.32%) as cell movement proteins, 63 (19.03%) as signal transduction proteins, 147 (44.4%) as proteases, 38 (11.5%) as enzyme regulator proteins, 21 (6.3%) as programmed cell death proteins, 12 (3.62%) as structural proteins and 59 (17.8%) as proteins with unknown molecular function.

CONCLUSIONShotgun proteomic strategy is a good method for protein identification. Annexin A, Annexin-associated proteins and the Ras-related protein Rab were the major members of the signal transducer proteins identified. Ca2+ and G protein signal pathways may play a most important role in the extracellular signal transduction into cells, but the interactions between these proteins remain unknown. The great quantity of enzymes and enzyme regulator proteins identified in the seminal plasma may be closely related with the maintenance of sperm motility and metabolism.