Previous Article | Next Article ![]()
Mol. Cell. Biol., 11 1997, 6663-6672, Vol 17, No. 11
J Ng, R Li, K Morgan and J Simon
The Drosophila extra sex combs (esc) protein, a member of the Polycomb
group (PcG), is a transcriptional repressor of homeotic genes. Genetic
studies have shown that esc protein is required in early embryos at about
the time that other PcG proteins become engaged in homeotic gene
repression. The esc protein consists primarily of multiple copies of the WD
repeat, a motif that has been implicated in protein-protein interaction. To
further investigate the domain organization of esc protein, we have
isolated and characterized esc homologs from divergent insect species. We
report that esc protein is highly conserved in housefly (72% identical to
Drosophila esc), butterfly (55% identical), and grasshopper (56%
identical). We show that the butterfly homolog provides esc function in
Drosophila, indicating that the sequence similarities reflect functional
conservation. Homology modeling using the crystal structure of another WD
repeat protein, the G-protein beta- subunit, predicts that esc protein
adopts a beta-propeller structure. The sequence comparisons and modeling
suggest that there are seven WD repeats in esc protein which together form
a seven-bladed beta- propeller. We locate the conserved regions in esc
protein with respect to this predicted structure. Site-directed mutagenesis
of specific loops, predicted to extend from the propeller surface,
identifies conserved parts of esc protein required for function in vivo. We
suggest that these regions might mediate physical interaction with esc
partner proteins.
Copyright © 1997, American Society for Microbiology
Evolutionary conservation and predicted structure of the Drosophila extra sex combs repressor protein
Department of Biochemistry, University of Minnesota, St. Paul 55108, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»