Fig. 2.

Conformation of loop J in the wild type and mutant structure. (A) Superimposition of the wild type and G178S PCNA mutant protein structures is shown with the Ser-178 substitution and Glu-113 represented in stick format and the hydrogen bond between them shown as black dots. The amino acid residues of loop J are indicated. (B) Close up view of loop J showing the electron density (level=2.0) for the G178S PCNA mutant protein and the backbone of the wild type and mutant proteins in ribbon representation. The distances between the wild type and mutant protein backbone are specified. (C) Side view of loop J with the position of the amino acid residues indicated.