Large-scale and high-confidence proteomic analysis of human seminal plasma

Here we report the high-confidence identification of 923 proteins in seminal fluid from a single individual. Fourier transform MS enabled parts per million mass accuracy, and two consecutive stages of MS fragmentation allowed confident identification of proteins even by single peptides. Analysis with GoMiner annotated two-thirds of the seminal fluid proteome and revealed a large number of extracellular proteins including many proteases. Other proteins originated from male accessory glands and have important roles in spermatozoan survival.This high-confidence characterization of seminal plasma content provides an inventory of proteins with potential roles in fertilization. When combined with quantitative proteomics methodologies, it should be useful for studies of fertilization, male infertility, and prostatic and testicular cancers.Seminal fluid is the liquid component of sperm, providing a safe surrounding for spermatozoa. At pH 7.35-7.50, it has buffering properties, protecting spermatozoa from the acidic environment of the vagina. It contains a high concentration of fructose, which is a major nutriment for spermatozoa during their journey in the female reproductive track. The complex content of seminal plasma is designed to assure the successful fertilization of the oocyte by one of the spermatozoa present in the ejaculum.Seminal plasma is a mixture of secretions from several male accessory glands, including prostate, seminal vesicles, epididymis, and Cowper's gland. The average protein concentration of human seminal plasma ranges from 35 to 55 g/l making it a rich as well as an easily accessible source for protein identification. Nevertheless, seminal plasma has the feature common to many other body fluids, that it is characterized by a high dynamic range of protein abundance, making low-abundance components difficult to analyze.In addition to the general physiological importance of knowing the composition of seminal fluid, medical interest centers on two main a