| MOLECULAR ARCHITECTURE OF THE SYNAPTONEMAL COMPLEX: SCP3 PROTEIN DOMAINS THAT ARE ESSENTIAL FOR POLYMERIZATION
Baier, A., Alsheimer, M., and Benavente, R.
Biocenter, University of Würzburg, , Germany
The synaptonemal complex (SC) is a karyoskeletal structure of meiotic cells that is critically involved in synaptic pairing and segregation of homologous chromosomes. The SC has a tripartite structure with a central region and two lateral elements (at which the chromatin of the respective homolog is attached). One major structural component of lateral elements of the mammalian SC is protein SCP3 (Lammers et al., 1994). This protein is composed of three domains: a central alpha-helical domain that has a length of 135 amino acids and is flanked by non-helical N- and C-termini which are 116 and 6 amino acids long, respectively. In a previous study (Yuan et al., 1998) it has been shown that both the N-terminus and the alpha-helix plus the C-terminus are required for SCP3 polymerization. For a more detailed study of the polymerization properties of this protein, we have transfected COS-7 cells with different SCP3 constructs. Here we show that most of the N-terminus is dispensable for proper polymerization of SCP3 molecules. In contrast, polymerization could be impaired if parts of the alpha-helix were deleted. We also identified two short sequences flanking the alpha-helix that are essential for polymerization, namely amino acids 87 to 105 of the N-terminus and the six amino acids of the C-terminus. Deletion of one of these two domains impairs SCP3 polymerization. The relevance of these two domains is emphasized by our analysis of data bases which showed that they are the best conserved SCP3 sequences throughout vertebrate evolution.
References:
Lammers J.H.M. et al.: Mol. Cell. Biol. 14:1137-1146, 1994
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