Cα-ribbon trace of the model of human R-type PK monomer. The color code is as for Fig 1: the N-terminal domain N is yellow, catalytic domain A is blue, domain B is orange, and the C-terminal twisted αβ-type domain C is pink. The positions of the amino acids 364 (G₁₀₉₁ to A mutation) and 510 (G₁₅₂₉ to A mutation) are indicated by red and green color, respectively. The active site bound pyruvate molecule taken from 1PKN⁹ is represented by pink space filling.