M. Yamazoe et al., Complex formation of MukB, MukE and MukF proteins involved in chromosome partitioning in Escherichia coli, EMBO J, 18(21), 1999, pp. 5873-5884
mukF, mukE and mukB genes are essential for the process of chromosome parti
tioning in Escherichia coil, We have studied protein-protein interactions a
mong MukB, MukE and MukF proteins by co-immunoprecipitation and sucrose gra
dient sedimentation experiments, using mukFEB null cells harboring plasmids
carrying the wild-type or mutant-type mukFEB operon, MukB forms a complex
with MukF and MukE, Analysis of mutant MukB proteins suggested that MukF an
d MukE bind the C-terminal globular domain of MukB, MukF is indispensable f
or an interaction between MukB and MukE; however, MukF itself is able to as
sociate with MukB even in the absence of MukE. We have also found that MukF
has a Ca2+-binding activity. Although purified MukF was able to make a com
plex either with MukE or MukB, a complex consisting of the three Muk protei
ns was barely detected in vitro. However, increasing the Ca2+ or Mg2+ conce
ntration in the reaction partially restored complex formation. This suggest
s that Ca2+ or Mg2+ may be required for the formation of a complex consisti
ng of the three Muk proteins, and thus may participate in a particular step
during chromosome partitioning.