Purification, crystallization and preliminary X-ray analysis of the PCNA2-PCNA3 complex from Sulfolobus tokodaii strain 7.

Crenarchaeal PCNA is known to consist of three subunits (PCNA1, PCNA2 and PCNA3) that form a heterotrimer (PCNA123). Recently, another heterotrimeric PCNA composed of only PCNA2 and PCNA3 was identified in Sulfolobus tokodaii strain 7 (stoPCNAs). In this study, the purified stoPCNA2-stoPCNA3 complex was crystallized by hanging-drop vapour diffusion. The crystals obtained belonged to the orthorhombic space groups I222 and P2(1)2(1)2, with unit-cell parameters a = 91.1, b = 111.8, c = 170.9 A and a = 91.1, b = 160.6, c = 116.6 A, respectively. X-ray diffraction data sets were collected to 2.90 A resolution for the I222 crystals and to 2.80 A resolution for the P2(1)2(1)2 crystals.