The human sperm proteome 2.0: An integrated resource for studying sperm functions at the level of posttranslational modification.

Various types of PTMs play important roles in the regulation of sperm proteins. However, most large-scale proteomic studies only focused on a single type of modification due to the limitation of enrichment methods. To investigate the complex composition of modified sperm proteins, we constructed the human sperm proteome 2.0 that integrated lysine acetylated, phosphorylated, N-linked glycosylated, and protein N-terminal acetylated proteins from previously published proteomic datasets. A total of 6069 modified sites on 2132 proteins were annotated. Functional enrichment analyses showed that different types of modified sperm proteins displayed different functional distributions. We found that acetylated, phosphorylated, and glycosylated proteins are more directly involved in sperm functions. While N-termnial acetylated proteins and nonmodified proteins appear to be more associated with the basic cellular functions. Thus, it is efficient to search for fertility-associated biomarkers in acetylated, phosphorylated, and glycosylated proteins. We also predicted modification cross-talks within the same proteins or between different proteins that provided potential hotspot targets for understanding the regulation of sperm functions via multiple modifications.