Crystal structure determination of HEX1 and human GEMININ 70-152

Abstract

Hex1 is the component of the Woronin body, which is functional in cell lysis to seal the septal pore in Neurospora crassa. The Hex1 crystal structure at 1.8 ?? reveals a three-dimensional protein lattice. Point mutation of the intermolecular contact residues results in Woronin bodies with soluble non-crystalline core, demonstrating that the Hex1 protein lattice is required for Woronin body function. The tertiary structure similarity between Hex1 and eukaryotic initiation factor 5A (eIF-5A) suggests that Hex1 might have evolved from the ancestral eIF-5A gene. Geminin plays an essential role in controlling the chromosome to replicate only once in the cell cycle. The crystal structure of the Cdt1 binding domain of Geminin at 2.0 ?? reveals that the fragment from residue 94 to 150 forms dimerized parallel coiled coil structure. Point mutation of residues critical for the coiled coil formation abolishes Geminina??s interaction with Cdt1 in vitro and in vivo as well as its ability to inhibit DNA replication.