The overall organization of cell division in Plasmodium is unique compared to 
that observed in model organisms because DNA replicates more than once per cell 
cycle at several points of its life cycle. The sequencing of the Plasmodium 
genome has also revealed the apparent absence of many key components (e.g. Cdt1, 
DDK and Cdc45) of the eukaryotic cell cycle machinery that are responsible for 
the formation of the pre-replication complex (pre-RC). We have characterized the 
Plasmodium falciparum minichromosome maintenance complex (MCM) that plays a key 
role in the transition of pre-RC to the RC. Similar to other eukaryotes, the 
Plasmodium genome encodes six MCM subunits. Here, we show that expression levels 
of at least three of the PfMCM subunits, the homologues of MCM2, MCM6 and MCM7, 
change during the intraerythrocytic development cycle, peaking in schizont and 
decreasing in the ring and trophozoite stages. PfMCM2, 6 and 7 subunits interact 
with each other to form a developmentally regulated complex: these interactions 
are detectable in rings and schizonts, but not in trophozoites. PfMCM2, 6 and 7 
subunits are localized in both cytosolic and nucleosolic fractions during all 
intraerythrocytic stages of P. falciparum development, with increased nuclear 
localization in schizonts. Only PfMCM6 is associated with the chromatin fraction 
at all stages of growth. No phosphorylation of PfMCM2, 6 and 7 was detected, but 
two as yet unidentified threonine-phosphosphorylated proteins were present in 
the complex, whose pattern of phosphorylation varied during parasite 
development.