This allows to insert folate computationally, or alternatively perhaps the binding of other small molecules

This allows to insert folate computationally, or alternatively perhaps the binding of other small molecules. and bioinformatics, Structural biology == Introduction == The successful fertilization in mammals requires sperm capacitation, acrosome TCPOBOP reaction, sperm penetration of the zona pellucida, specific sperm-egg acknowledgement and finally membrane fusion with the egg1,2. The sequence of all those events must be highly specific, precisely coordinated in time and space, and be species-selective to ensure that only one sperm fertilizes the egg. Once a sperm has joined the perivitelline space of an egg, the first known specific physical link is usually formed between the two opposing membranes, more specifically between the two proteins, IZUMO1 and JUNO. IZUMO1 is a trans-membrane protein presented around the sperm surface3, while its counterpart, JUNO (also called IZUMO1 Rabbit Polyclonal to NOM1 Receptor, IZUMO1R) is a GPI (glycosylphosphatidylinositol)-anchored membrane protein on the surface of the egg4. Their transient complexation is usually thought to initiate the acknowledgement and adhesion process between the two gametes, possibly triggering their fusion. No clear mechanism has been recognized so far, although different conversation models were proposed58. The possibility of a fusogenic activity of IZUMO1 has been discussed, but the evidence is still marginal. Experiments on normally non-fusing, innate HEK293 cells showed that simply the expression of JUNO and IZUMO1 is TCPOBOP not enough to initiate the membrane fusion process4, despite recent reports that IZUMO1 independently of JUNO might serve as unilateral fusogen9. A few other additional molecular players were suggested to be crucially involved in this process1013, yet their exact TCPOBOP binding partners in the context of inter-gamete interactions have not been established8. Also, first efforts to identify successful JUNO-IZUMO1 interface inhibitors have been undertaken, regretfully, none of the small molecule candidates were confirmed to block this conversation14. This all suggests that far too little information of the hydrated structures is available to understand the crucial first actions of gamete fusion. Given the lack of a conclusive molecular picture how the JUNO-IZUMO1 binding might initiate gamete fusion, we performed all-atom molecular dynamics (MD) and simulated the proteins alone, or in a complex with each other, in a box filled with explicit water molecules and ions. Such simulations allow to extract information how hydration of known protein crystal structures might switch the dynamics TCPOBOP of the JUNO-IZUMO1 interactions, thereby providing insights into the locations and lifetimes of crucial bonds, information that is not easily accessible via traditional experimental methods of structural biology. MD is thus particularly well-suited to observe the time-dependent changes of the protein complexation and to capture new biologically relevant structural alterations15,16. Our MD simulations were performed around the human JUNO-IZUMO1 complex, hydrated in explicit water, and for the proteins alone, using the wild type proteins whose structures have been recently resolved via crystallization6,7. To validate the predictive power of our MD simulations, we have also simulated the complex after introducing two in silico point mutations. The first one is known to abolish the JUNO-IZUMO1 conversation in vitro: IZUMO1s TRP148ALA located in the binding interface6,7. The second is JUNOs fertility-relevant mutation HIS177GLU17. As IZUMO1 in the crystal structures has been seen in two conformations, one that has a straight conformation like in the complex with JUNO7, and the second, where IZUMO1 adapts a bent conformation, also referred to as the boomerang conformation6. We asked how the shape of IZUMO1 might impact its binding to JUNO and whether the presence of divalent ions might stabilize one versus the other conformation. As the fusion of the first sperm with an egg is known to induce a zinc TCPOBOP spark18,19, characterized by the rapid release of Zn2+by the egg, our focus was then to study the conversation between Zn2+ions and IZUMO1, and whether it could potentially play additional functions in fertilization. Looking into this question is also important considering.