6h86 | pdb_00006h86
Rebuilt and re-refined PDB entry 4R3Q: Crystal structure of SYCE3
Structural highlights
Function[SYCE3_MOUSE] Major component of the transverse central element of synaptonemal complexes (SCS), formed between homologous chromosomes during meiotic prophase. Required for chromosome loading of the central element-specific SCS proteins, and for initiating synapsis between homologous chromosomes. Chromosome loading appears to require SYCP1. Required for fertility. May play a role in apoptosis of spermatogenic cells and pathogenesis of cryptorchidism.[1] [2] Publication Abstract from PubMedThe synaptonemal complex (SC) is a supramolecular protein assembly that mediates homologous chromosome synapsis during meiosis. This zipper-like structure assembles in a continuous manner between homologous chromosome axes, enforcing a 100-nm separation along their entire length, and providing the necessary three-dimensional framework for crossover formation. The mammalian SC comprises eight components-synaptonemal complex protein 1-3 (SYCP1-3), synaptonemal complex central element protein 1-3 (SYCE1-3), testis expressed 12 (TEX12), and six6 opposite strand transcript 1 (SIX6OS1)-arranged in transverse and longitudinal structures. These largely alpha-helical, coiled-coil proteins undergo heterotypic interactions, coupled with recursive self-assembly of SYCP1, SYCE2-TEX12, and SYCP2-SYCP3, to achieve the vast supramolecular SC structure. Here, we report a novel self-assembly mechanism of the SC central element component SYCE3, identified through multi-angle light scattering and small-angle X-ray scattering (SAXS) experiments. These analyses revealed that SYCE3 adopts a dimeric four-helical bundle structure that acts as the building block for concentration-dependent self-assembly into a series of discrete higher-order oligomers. We observed that this is achieved through staggered lateral interactions between self-assembly surfaces of SYCE3 dimers and through end-on interactions that likely occur through intermolecular domain swapping between dimer folds. These mechanisms are combined to achieve potentially limitless SYCE3 assembly, particularly favoring formation of dodecamers of three laterally associated end-on tetramers. Our findings extend the family of self-assembling proteins within the SC and reveal additional means for structural stabilization of the SC central element. A molecular model for self-assembly of the synaptonemal complex protein SYCE3.,Dunne OM, Davies OR J Biol Chem. 2019 Apr 25. pii: RA119.008404. doi: 10.1074/jbc.RA119.008404. PMID:31023827[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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