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FYVE-related domain found in synaptotagmin-like protein 4 (Slp4) and similar proteins Slp4, also termed exophilin-2, or granuphilin, has been characterized as a regulator of the release of insulin granules from pancreatic beta-cells and dense core granules from PC12 neuronal cells by binding to Rab27A , and amylase granules from parotid gland acinar cells through interaction with syntaxin-2/3 in a Munc18-2-dependent manner on the apical plasma membrane. It can binds to syntaxin 2 in parotid acinar cells. It is also involved in granule transport by recruitment of the motor protein myosin Va. Moreover, it requires Rab8 to increase granule release in platelets. Slp4 contains an N-terminal Slp homology domain (SHD) and C-terminal tandem C2 domains. The Slp homology domain (SHD) consists of two conserved regions, designated SHD1 (Slp homology domain 1) and SHD2, which may function as protein interaction sites. The SHD1 and SHD2 of Slp4 are separated by a putative FYVE zinc finger, which resembles a FYVE-related domain that is structurally similar to the canonical FYVE domains but lacks the three signature sequences: an N-terminal WxxD motif (x for any residue), the central basic R(R/K)HHCRxCG patch, and a C-terminal RVC motif.
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