Archaeal MCM has separable processivity, substrate choice and helicase domains.

Area of Science:

• Molecular biology
• Biochemistry
• Structural biology

Background:

• The mini-chromosome maintenance (MCM) complex is a key replicative helicase in archaea and eukaryotes.
• Understanding MCM complex function requires dissecting the roles of its structural modules.

Purpose of the Study:

• To functionally dissect the roles of the three principal structural modules of the homomultimeric MCM complex from Sulfolobus solfataricus.
• To analyze the isolated central AAA+ domain for its intrinsic enzymatic activities.

Main Methods:

• Functional dissection of MCM structural modules.
• In vitro biochemical assays including ATPase and helicase activity measurements.
• Reconstitution experiments with isolated MCM domains.

Main Results:

• The central AAA+ domain possesses intrinsic ATPase and helicase activity, representing the minimal helicase domain.
• The N-terminal half stimulates helicase activity and influences processivity and substrate selection.
• The C-terminal helix-turn-helix domain negatively impacts helicase activity.

Conclusions:

• The AAA+ domain is the minimal catalytic unit for MCM helicase activity.
• Inter-domain communication within the MCM complex regulates its function.
• Distinct structural modules contribute to the regulation of helicase activity and substrate specificity.