1pk3
From Proteopedia
Scm SAM domain
Overview
The polycomb group proteins are required for the stable maintenance of gene repression patterns established during development. They function as part of large multiprotein complexes created via a multitude of protein-protein interaction domains. Here we examine the interaction between the SAM domains of the polycomb group proteins polyhomeotic (Ph) and Sex-comb-on-midleg (Scm). Previously we showed that Ph-SAM polymerizes as a helical structure. We find that Scm-SAM also polymerizes, and a crystal structure reveals an architecture similar to the Ph-SAM polymer. These results suggest that Ph-SAM and Scm-SAM form a copolymer. Binding affinity measurements between Scm-SAM and Ph-SAM subunits in different orientations indicate a preference for the formation of a single junction copolymer. To provide a model of the copolymer, we determined the structure of the Ph-SAM/Scm-SAM junction. Similar binding modes are observed in both homo- and heterocomplex formation with minimal change in helix axis direction at the polymer joint. The copolymer model suggests that polymeric Scm complexes could extend beyond the local domains of polymeric Ph complexes on chromatin, possibly playing a role in long range repression.
About this Structure
1PK3 is a Single protein structure of sequence from Drosophila melanogaster. Full crystallographic information is available from OCA.
Reference
Structural organization of a Sex-comb-on-midleg/polyhomeotic copolymer., Kim CA, Sawaya MR, Cascio D, Kim W, Bowie JU, J Biol Chem. 2005 Jul 29;280(30):27769-75. Epub 2005 May 19. PMID:15905166 Page seeded by OCA on Sat May 3 05:10:38 2008
