Download MendeleyBiochemical and Structural Characterization of Apolipoprotein A-I Binding Protein, a Novel Phosphoprotein with a Potential Role in Sperm Capacitation.
Jha, K.N., Shumilin, I.A., Digilio, L.C., Chertihin, O., Zheng, H., Schmitz, G., Visconti, P.E., Flickinger, C.J., Minor, W., Herr, J.C.(2008) Endocrinology 149: 2108-2120
- PubMed: 18202122
- DOI: https://doi.org/10.1210/en.2007-0582
- Primary Citation of Related Structures:
2DG2, 2O8N - PubMed Abstract:
The physiological changes that sperm undergo in the female reproductive tract rendering them fertilization-competent constitute the phenomenon of capacitation. Cholesterol efflux from the sperm surface and protein kinase A (PKA)-dependent phosphorylation play major regulatory roles in capacitation, but the link between these two phenomena is unknown. We report that apolipoprotein A-I binding protein (AI-BP) is phosphorylated downstream to PKA activation, localizes to both sperm head and tail domains, and is released from the sperm into the media during in vitro capacitation. AI-BP interacts with apolipoprotein A-I, the component of high-density lipoprotein involved in cholesterol transport. The crystal structure demonstrates that the subunit of the AI-BP homodimer has a Rossmann-like fold. The protein surface has a large two compartment cavity lined with conserved residues. This cavity is likely to constitute an active site, suggesting that AI-BP functions as an enzyme. The presence of AI-BP in sperm, its phosphorylation by PKA, and its release during capacitation suggest that AI-BP plays an important role in capacitation possibly providing a link between protein phosphorylation and cholesterol efflux.
Organizational Affiliation:
Center for Research in Contraceptive and Reproductive Health, Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908, USA.
