X.-P. Kong, R. Onrust, M.J. O'Donnell and J. Kuriyan. (1992) Three-dimensional structure of the beta subunit
of E. coli DNA Polymerase III Holoenzyme: a sliding DNA clamp Cell, 69, 425-437.
This paper presented the first crystal structure of a "processivity factor"
for a DNA polymerase.
DNA polymerases that replicate entire genomes during cell division are able
to move along DNA very rapidly without
letting go. Mike O'Donnell (HHMI, Rockefeller University) showed that the tight
association with DNA during
replication depends upon the processivity factor, a protein assembly that holds
the polymerase onto DNA
due to a topological linkage. The processivity factor is also known as a "sliding
DNA clamp"
(a term introduced by Huang, Hearst and Alberts).
By determining the three-dimensional structure of the processivity factor of
bacterial DNA polymerase (the beta-subunit),
we established (in collaboration with Mike O'Donnell) that the processivity
factor is a ring-shaped and
highly symmetrical assembly through which DNA can be threaded.
The high symmetry of the beta-subunit assembly allowed a connection to be made
between the architecture of this
ring-shaped assembly seen in bacteria and the processivity factors of eukaryotic
(including human) and
bacteriophage DNA polymerases.