The C-clamp domain is sufficient for binding to the Helper site.

<p>(A) EMSA showing that a His-tagged C-clamp domain can bind to a DNA probe containing a Helper site, while a C-clamp protein containing two mutations in the domain (K2A, R4E; same as mutant 5 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086180#pone-0086180-g003" target="_blank">Figure 3A</a>) has greatly reduced binding. Neither protein bound a probe lacking a Helper site. For each binding reaction 50 and 100 pmoles of protein and 20 fmoles of oligonucleotide were used. (B,C) Quantification of the EMSA data using the Licor system. The bar graph results are the means of at least three separate binding reactions±SD. See Materials and Methods for details.