Which protein complex is necessary for the fusion of vesicles with their target membranes?

The process of vesicle fusion with target membranes is critically dependent on the SNARE protein complex. SNAREs, which can be found on both the vesicle (v-SNAREs) and the target membrane (t-SNAREs), facilitate the specific recognition and docking of vesicles to their corresponding target membranes. When a vesicle approaches its target, the interacting SNAREs undergo a conformational change that brings the two membranes into close proximity, ultimately leading to the merging of the lipid bilayers and the release of the vesicular contents into the target compartment.

The role of SNAREs is essential because they not only ensure the specificity of vesicle targeting—helping to prevent misdirection of cargo—but also drive the actual fusion process. This is governed by the energy released during the formation of the SNARE complex, which helps to overcome the energy barrier associated with the fusion of the lipid membranes.

While other options mention various protein complexes that are involved in vesicle transport or regulation, none are directly responsible for the membrane fusion process itself as SNAREs are. Coat proteins assist in the budding of vesicles from the donor membrane but do not facilitate fusion. Rab proteins are involved in the docking process by recruiting the SNAREs and