Subunit organization of Mcm2-7 and the unequal role of active sites in ATP hydrolysis and viability.

  • Bochman M
  • Bell S
  • Schwacha A
  • 70

    Readers

    Mendeley users who have this article in their library.
  • 72

    Citations

    Citations of this article.

Abstract

The Mcm2-7 (minichromosome maintenance) complex is a toroidal AAA(+) ATPase and the putative eukaryotic replicative helicase. Unlike a typical homohexameric helicase, Mcm2-7 contains six distinct, essential, and evolutionarily conserved subunits. Precedence to other AAA(+) proteins suggests that Mcm ATPase active sites are formed combinatorially, with Walker A and B motifs contributed by one subunit and a catalytically essential arginine (arginine finger) contributed by the adjacent subunit. To test this prediction, we used copurification experiments to identify five distinct and stable Mcm dimer combinations as potential active sites; these subunit associations predict the architecture of the Mcm2-7 complex. Through the use of mutant subunits, we establish that at least three sites are active for ATP hydrolysis and have a canonical AAA(+) configuration. In isolation, these five active-site dimers have a wide range of ATPase activities. Using Walker B and arginine finger mutations in defined Mcm subunits, we demonstrate that these sites similarly make differential contributions toward viability and ATP hydrolysis within the intact hexamer. Our conclusions predict a structural discontinuity between Mcm2 and Mcm5 and demonstrate that in contrast to other hexameric helicases, the six Mcm2-7 active sites are functionally distinct.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Authors

  • Matthew L Bochman

  • Stephen P Bell

  • Anthony Schwacha

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free