A biochemically active MCM-like helicase in Bacillus cereus.
The mini-chromosome maintenance (MCM) proteins serve as the replicative helicases in archaea and eukaryotes. Interestingly, an MCM homolog was identified, by BLAST analysis, within a phage integrated in the bacterium Bacillus cereus (Bc). BcMCM is only related to the AAA region of MCM-helicases; the typical amino-terminus is missing and is replaced by a segment with weak homology to primases. We show that BcMCM displays 3'-->5' helicase and ssDNA-stimulated ATPase activity, properties that arise from its conserved AAA domain. Isolated BcMCM is a monomer in solution but likely forms the functional oligomer in vivo. We found that the BcMCM amino-terminus can bind ssDNA and harbors a zinc atom, both hallmarks of the typical MCM amino-terminus. No BcMCM-catalyzed primase activity could be detected. We propose that the divergent amino-terminus of BcMCM is a paralog of the corresponding region of MCM-helicases. A divergent amino terminus makes BcMCM a useful model for typical MCM-helicases since it accomplishes the same function using an apparently unrelated structure.
Samuels
Martin
M
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Gulati
Gaurav
G
Shin
Jae-Ho
JH
Opara
Rejoice
R
McSweeney
Elizabeth
E
Sekedat
Matt
M
Long
Stephen
S
Kelman
Zvi
Z
Jeruzalmi
David
D
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001409:Bacillus cereus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000737:chemistry / Q000378:metabolism*; D019915:DNA Primase / Q000032:analysis; D004277:DNA, Single-Stranded / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015032:Zinc / Q000378:metabolism
D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D000255:Adenosine Triphosphate; D004247:DNA; D019915:DNA Primase; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; D015032:Zinc