As expected, these two mutant proteins exhibited significant decreases in phospholipid binding in the presence of various concentrations of Ca2+ when compared with Ann5. The reduction of the mutants binding to phospholipids presents two possibilities. First, the glycine residue in the endonexin motif of Ann5 may be the critical part of the phospholipid-binding sites and other amino acids residues may be involved in assembly of the intact site. Second, the crucial glycine residue with other amino acids may stabilize the conformation of the binding between Ann5 and phospholipids. The two different binding modes for Ann5 are most likely interconnected because annexin-membrane association has been demonstrated to be highly sequential and complicated and show consonance with respect to calcium. Additionally, Hofmann et al. Clinofibrate found that another unique feature of plant annexins is their tendency to form calciumindependent oligomers. Such a structure would be facilitate the interaction between Ann5 and membranes in low calcium ion concentrations and be suitable for the complex physical processes in pollen cells. Several vertebrate annexins, such as Annexin A2, which is required for the actin-dependent, apical transport of raftassociated sucrase-isomaltase-carrying vesicles in polarized epithelial cells,Fluocinonide participate in actin remodeling. Although many plant annexins possess the IRI motif, which is necessary for F-actin binding to myosin, only a few have been found to bind filamentous actin, and this interaction appears to be species specific. For example, Mimosa annexin induced F-actin to form thick bundles in the presence of Ca2+ in vitro and was shown to be involved in pulvinar nyctinastic movements. Annexins p34 and p35 from tomato were found to bind to F-actin, but not globular actin, and this interaction was calcium- and pH-dependent. Two annexins from zucchini associated with the membrane and bound to zucchini-derived F-actin. Based on the results of high-speed co-sedimentation assays, the recombinant Ann5 studied here bound to F-actin in vitro. Furthermore, the Ann5 sequence contained a partially conserved F-actin-binding motif, IQI, in repeat III.