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PCNA
complexed with DNA has been studied to gain insight into the
clamp-loading process. DNA is shown in purple.
Residues that appeared to contact the DNA in crystallographic
data and modeling are shown in black. (Lys 13, Arg 14, Lys 146,
and Arg 149 of subunit A and Lys 146 and Arg 149 of subunit C).
However, mutating these residues did not affect clamp loading,
measured by RFC ATPase activity. Instead, mutations in the
following residues shown in cyan had a large effect on clamp
loading. (Lys 20, Lys 77, Arg 80, and Arg 149 of subunit A).
The only overlap between these two groups is Arg 149 of subunit
A, colored green.
Further studies will be necessary to elucidate the mechanism of
these residues in clamp loading. |