assembles with membrane proteinsSyntaxin and SNAP 25 (Oyler et al.
1989; Bennett et al. 1992) and form aternary complex (Hanson et al. 1997). These proteins are the receptors for NSF(N-ethylmaleimide-sensitive factor) and SNAPs (Soluble NSF attachment proteins)and so-called SNAREs (SNAP receptors) (Söllner et al.1993a, 1993b). TheseSNARE proteins located at vesicles (v-SNARE) interacts with proteins at thetargeted membrane (t-SNARE) and help in fusion (Söllner et al. 1993a; Rothman and Warren,1994).
SNAREs that are aligned parallel to their transmembrane anchors duringdocking (Otto et al. 1997), connects two membranes thereby zippering of v-SNAREand t-SNARE (Hanson et al. 1997). The ATPase activity of NSF dissociates theternary SNARE complex (Söllner et al. 1993a; Hayashi et al.1995). This leads to the conformational change of associated proteins andinduce fusion of secretory vesicle to the target membrane (Hanson et al. 1997).
This activity of NSF could be to dock new secretory vesicles thereby recruitingnew SNARE complexes (Hanson et al. 1997). The importance of exocyst in cellular processesis inevitable as it plays key role in exocytosis thereby mediating SNAREmediated membrane fusion (He and Guo, 2009). The exocyst complex acts as asignal receiver for various signaling pathways, help tether vesicles at thereceptor membrane and mediate fusion by inducing formation of SNARE assembly (Heand Guo, 2009; Žárský et al. 2013).Various experiments have been done to prove its efficacy for growth, migration,repair and defense by increasing or decreasing proteins, breaking theassociation among the subunits and its associated proteins that are necessaryin this process (Novick et al.
1980; Hala et al. 2002; He et al. 2007; Zhang etal. 2008). The exocyst mutants show secretion defects and intracellularaccumulation of the secretory vesicles (Novick et al. 1980; Guo et al. 1999; Zhanget al. 2005, He et al.
2007; Zhang et al. 2008; Heider and Munson, 2012). Themutation in exocyst subunit exo70 shows defects in secretion of secretoryvesicles (He et al. 2007) that transport endoglucanase Bg12 required for cellmembrane expansion and cell wall remodeling (He and Guo, 2009). Impairing theconnection of sec 3 and exo 70 with PI (4,5) P2 halts the fusionprocess leading to cell death (He et al. 2007; Zhang et al. 2008).
As exocystmediates the SNARE assembly, their mutants failed to form SNARE complex (Groteet al. 2000).